Data Recovery Advisor

ABSTRACT

A computer is programmed to identify failures and perform recovery of data. Specifically, in several embodiments, the computer is programmed to automatically check integrity of data in a storage structure to identify a set of failures related to the storage structure. The computer is further programmed in some embodiments to identify, based on one failure in the set of failures, a group of repairs to fix that one failure. Each repair in the group of repairs is alternative to another repair in the group. The computer is also programmed in some embodiments to execute at least one repair in the group of repairs, so as to generate corrected data to fix the one failure. In certain embodiments, the corrected data is stored in non-volatile storage media of the computer.

CROSS-REFERENCE TO PROVISIONAL APPLICATION

This application claims priority under 35 USC § 119 (e) from aprovisional application No. 60/981,469 filed on Oct. 19, 2007 having thetitle “Recognizing And Repairing Data Failures”, filed by Mark Dilman etal, Attorney Docket ORA-2006-163-01 US, which is incorporated byreference herein in its entirety.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and incorporates by reference herein intheir entirety, each of the following two commonly owned andconcurrently filed applications, both having Mark Dilman as the firstnamed inventor:

-   -   a. U.S. patent application Ser. No. ______ having the title        “Repair Planning Engine For Data Corruptions”, Attorney Docket        OID-2006-303-01 US; and    -   b. U.S. patent application Ser. No. ______ having the title        “Data Corruption Diagnostic Engine”, Attorney Docket        OID-2006-295-01 US.

BACKGROUND

It is well known in the art for computers to encounter faulty hardwareand/or software during storage and retrieval of data. For example, anerror may arise when the computer unexpectedly encounters a breakdown inhardware, e.g. in magnetic media (such as a hard disk) where the data isstored. In addition to faulty hardware, errors can also arise due tobugs in software, e.g. an application program may overwrite data ofanother application program or an application program may improperly usean interface (API) of the underlying operating system to cause wrongdata to be stored and/or retrieved. These faults are called datacorruptions. Therefore, a fault can arise during normal operation in anycomponent of a system. Examples of components are network interfacecircuitry, disks, operating system, application programs, cache, devicedriver, storage controller, etc.

Some application programs, such as database management systems (DBMS),may generate errors when data corruptions are detected, e.g. if apreviously-stored checksum does not match a newly-calculated checksum. Asingle fault (also called “root” cause) can result in multiple failureswith different symptoms; moreover, a single symptom can correspond tomultiple failures. Knowing a symptom or a root cause of a failure issometimes not enough for a human to formulate one or morerecommendations to repair the failed hardware, software or data.

Manually reviewing such errors (by a system administrator) andidentifying one or more faults which caused them to be generated canbecome a complex and time-consuming task, depending on the type andnumber of errors and faults. Specifically, the task is complicated bythe fact that some errors are not generated immediately when a faultoccurs, e.g. a fault may cause corrupted data to be stored to disk andeven backed up, with errors due to the fault being generated a long timelater, when the data is read back from disk. Furthermore, errors due toa single fault do not necessarily appear successively, one afteranother. Sometimes errors due to multiple faults that occur concurrentlyare interspersed among one another, which increases the task'scomplexity. Also, information about some faults is interspersed amongdifferent types of information, such as error messages, alarms, tracefiles and dumps, failed health checks etc. Evaluating such informationand correlating them is a difficult task that is commonly done manuallyin prior art, which is error prone and time consuming. Error correlationcan be done automatically instead of manually. Systems for automaticerror correlation are commonly referred to as “event correlationsystems” (see an article entitled “A Survey of Event CorrelationTechniques and Related Topics” by Michael Tiffany, published on 3 May2002). However, such systems require a user to manually specifycorrelation rules that capture relationships between errors. Such rulesapplied to data storage systems that generate many types of errors undermany different failure scenarios can be very complex. They are alsooften based on a temporal ordering of errors that might not be correctlyreported by a data storage system. This makes such systems prone togenerating wrong results, false positives and false negatives.

Moreover, any new error type added to the system or any new failurescenario require reconsideration of the correlation rules that makesthem difficult to maintain and, therefore, even less reliable. Finally,an error correlation system is intended to find a “root cause” faultthat could be different from the data failure because it does notindicate which data is corrupted and to which extent. Moreover, evenafter a fault has been identified correctly by a system administrator,repairing and/or recovering data manually requires a high degree oftraining and experience in using various complex tools that are specificto the application program. For example, a tool called “recoverymanager” (RMAN) can be used by a database administrator to performbackup and recovery operations for the database management system Oracle10g. Even though such tools are available, human users do not havesufficient experience in using the tools because data faults do notoccur often. Moreover, user manuals and training materials for suchtools usually focus on one-at-a-time repair of each specific problem,although the user is typically faced with a number of such problems.Also, there is often a high penalty paid by the user for making poordecisions as to which problem to address first and which tool to use, interms of increased downtime of the application program's availability,and data loss. To sum up, fault identification and repair of data in theprior art can be one of the most daunting, stressful and error-pronetasks when performed manually.

SUMMARY

A computer is programmed in accordance with the invention to use asoftware tool (called “data recovery advisor”) to identify failures andperform recovery of data. Specifically, in several embodiments, thecomputer is programmed to automatically check integrity of data in astorage structure to identify a set of failures related to the storagestructure. The computer is further programmed in some embodiments toidentify, based on one failure in the set of failures, a group ofrepairs to fix that one failure. Each repair in the group of repairs isalternative to another repair in the group. The computer is alsoprogrammed in some embodiments to execute at least one repair in thegroup of repairs, so as to generate corrected data to fix the onefailure. In certain embodiments, the corrected data is stored innon-volatile storage media of the computer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates, in a high level flow chart, acts performed by adata recovery advisor in some embodiments of the invention, to identifyfailures and perform recovery of data for any software program.

FIGS. 1B and 1C illustrate, in high level flow charts, acts performed bytwo alternative embodiments of the data recovery advisor of thisinvention.

FIGS. 2A and 2C illustrate, in flow charts, acts performed by adiagnostic module to implement act 101 of FIGS. 1A-1C, in accordancewith the invention.

FIG. 2D illustrates how a failure record is created, stored andretrieved.

FIG. 2B illustrates a mapping in main memory, of error types toidentifiers of diagnostic procedures, used by act 101 of FIGS. 1A-1C, inaccordance with the invention.

FIG. 2E illustrates a record for a failure stored in a repository 196within a storage device 810, by act 101 of FIGS. 1A-1C, in accordancewith the invention.

FIG. 3A illustrates a mapping of failure types to three groups that havea predetermined order relative to one another, for use in formulating asequence of repairs to satisfy prerequisites arising from dependenciesbetween repairs, in certain embodiments of the invention.

FIG. 3B illustrates, in a high level flow chart, a method 310 that isperformed in some embodiments to create a repair plan using the mappingof FIG. 3A.

FIG. 3C illustrates a mapping of repair type to templates for use by themethod of FIG. 3B to generate repairs, and a repair plan that is createdin some embodiments of the invention.

FIG. 3D illustrates, in an intermediate level flow chart, oneillustrative implementation of the method 310 of FIG. 3B.

FIG. 4A illustrates, in another flow chart, acts performed by a datarecovery advisor (DRA) in a database embodiment of the invention.

FIG. 4B illustrates a mapping of failure types to six groups, five ofwhich have a predetermined order relative to one another, which are usedby the method of FIG. 4A.

FIG. 4C illustrates, in a block diagram, various components that areused to implement two portions, namely a server-side portion and aclient-side portion of the data recovery advisor (DRA) of FIG. 4A.

FIG. 4D illustrates, in a flow chart, an implementation of consolidationact 406A of FIG. 4A in some embodiments of the invention.

FIGS. 5A-5P illustrate screens of a graphical user interface that areused by a database administrator to interact with the data recoveryadvisor of FIG. 4A to identify and correct exemplary failures in anillustrative embodiment of the invention. Note that in FIG. 5M of analternative embodiment, the text after generated recovery advice of: “ismade more descriptive, to says “The repair includes media recovery withno data loss” instead of just “NO DATALOSS” as shown in FIG. 5M.

FIGS. 6A-6H illustrate additional screens of the type shown in FIGS.5A-5P used by the data recovery advisor of FIG. 4A to identify andcorrect additional failures in the illustrative embodiment of theinvention.

FIGS. 7A-7G illustrate use of a command line interface by a databaseadministrator to interface with the data recovery advisor of FIG. 4A toidentify and correct the failures described in reference to FIGS. 5A-5P.Note that in FIG. 7B, the display shown is generated by a human usertyping an ADVICE command at the command line prompt (not shown).

FIG. 8 illustrates, in a high level block diagram, hardware included ina computer that may be used to implement the embodiments of FIGS. 4A and4B in some illustrative implementations of the invention.

DETAILED DESCRIPTION

In many embodiments, a data storage system 10 (FIG. 1A) is implementedwithin a computer system 800 illustrated in FIG. 8, and programmed inaccordance with the invention to use a software tool 100, also hereincalled “data recovery advisor” or abbreviated as DRA. In certainembodiments, the data recovery advisor automatically responds to errorsoccurring within data storage system 10 by running diagnostic proceduresthat check integrity of one or more components within data storagesystem 10. More specifically, in view of one or more reasons describedabove in paragraph [0005] of the Background Section above, a datarecovery advisor (DRA) of some embodiments does not rely on correlatingerrors. Instead the DRA of these embodiments uses errors as a “hint” tostart (or trigger) comprehensive integrity checks of system component(s)associated with the error. Such checks (e.g. a data block integritycheck) in data storage systems usually can be fast (relative to errorcorrelation) and their execution does not consume a lot of systemresources. A medical analogy to certain DRA's integrity checking is asfollows: if a CT Scan were cheap, doctors would prefer to always use itto diagnose a disease, and patient's symptoms would just be used todetermine which body part(s) to scan.

Examples of data storage system 10 for which a DRA of the type describedherein can be used include file systems, storage arrays, file servers,and database management systems. Data storage system 10 includes asoftware program 11 that stores data 15 persistently in storage device12 (implemented by storage device 810 in FIG. 8), which may be, forexample, a hard disk, a flash memory or a tape. While storing data 15 tostorage device 12 and/or during retrieval of data 15 from storage device12, software program 11 may encounter one or more error(s) 13, such asnot being able to access a file normally used by software program 11.

Note that software program 11 of FIG. 1A may implement any functionalitywhen programmed into computer system 800, such as an operating system,and/or any application program. Accordingly, a data recovery advisor 100of the type illustrated in FIG. 1A is prepared and used in someembodiments, to repair errors in data accessed by (i.e. read by and/orwritten by) an operating system (which is the software program 11 ofthese embodiments). In other embodiments, data recovery advisor 100 isprepared and used in some embodiments, to repair errors in data accessedby an application program, such as video game software (which istherefore the software program 11 of these embodiments).

In some embodiments, errors 13 are persistently stored by softwareprogram 11 in a repository (not shown in FIG. 1A; see storage device 810in FIG. 8), and the stored errors are later used to identify and fixfailures 193 and/or to recover data 15 that has become corrupted and/ornot available for some reason. In certain embodiments, errors 13 arestored only temporarily for a short period of time (e.g. less than aminute), in volatile memory of computer system 800, such as main memory806 (FIG. 8). Note that computer system 800 may include one or morecomputers (illustrated by dashed boxes), depending on the embodiment.The just-described temporarily-stored errors may constitute transienterrors, of the type likely to be unavailable in future, and for thisreason in some embodiments, an act 101 (FIG. 1A) is performed inresponse to occurrence of one or more errors, although in otherembodiments act 101 can be performed in response to a command from ahuman user, and alternatively act 101 can be performed on a pre-setschedule.

In act 101, data recovery advisor 100 checks integrity of certainstructure(s) which are used to store data 15 in storage device 12, andif any failures are found by integrity checking, then data recoveryadvisor 100 persistently stores the failure(s) along with one or moreattributes and parameters that uniquely define the failure(s) in arecord (or other such data structure) in a repository 196 in a storagedevice 810 of computer system 800, such as a hard disk. Attributes arecertain properties which happen to be common to all failures, whereasparameters are other properties which depend on the specific type offailure, with some types of failures having no parameters and othertypes of failures having any number of parameters (e.g. 1, 3, 5parameters). Attributes can be, for example, time of occurrence, failuretype, failure status (e.g. open/closed), and failure priority (e.g.critical/high/low). Parameters depend on each failure's type, forexample a file missing failure may have a single parameter which is aunique identifier of the file, such as file name and location (e.g URL).Similarly, a block corrupt failure may have as its two parameters (a) aunique identifier of the block within a file, and (b) a uniqueidentifier of the file containing the block.

In some embodiments, act 101 uses a reverse object name lookup table 19which is prepared ahead of time, to associate data blocks back to theobjects to which the blocks belong. The reverse object name lookup tableis referred to as metadata since it stores information about the data inthe storage system. This allows you to tell that block 255 on device 7is really the jpeg file ‘Spain bell tower 2007.jpg’. In some databases,this reverse object lookup table might be part of the metadata that isstored in the data dictionary. Reverse object name lookup table 19 ispre-created by software program 11 so that it is usable off-line, sothat the metadata is available to act 101 for use in interpreting errorsand/or generating failures based on data 15, even when software program11 is not running.

Specifically, after logging one or more of errors 13, software program11 may crash and stop running, or if running may become otherwiseinoperable (e.g. “hang”). Accordingly, an off-line dictionary 14 is usedby some embodiments of act 101 to lookup metadata that may be requiredto diagnose errors 13. In other embodiments, the off-line dictionary isnot used to diagnose errors, and instead it is used to determine impactof known failures. Off-line dictionary 14 may be kept in a storagedevice 18 that is different from storage device 12 in which data 15 iskept as shown in FIG. 1A, or alternatively a single storage device maybe used to store both data 15 and off-line dictionary 14. Off-linedictionary 14 is also used in some embodiments to formulate repairs tobe performed, and/or to perform repairs. In some embodiments, dictionary14 forms a portion of data 15, although inaccessibility of data 15causes inability to diagnose some errors 13.

Note that failures are not necessarily found after performance of act101 by the programmed computer, e.g. there may be no failure if an errorthat triggered act 101 arose from an underlying fault that becomes fixedwhen act 101 is performed (fixed either automatically or by humanintervention). Alternatively, in some situations, an error thattriggered act 101 may have been a false positive, i.e. there may be nounderlying fault. Accordingly, performing act 101 in response to anerror has the benefit of screening out the error if it happens to be afalse positive. In act 101 of some embodiments, data recovery advisor100 examines one or more structure(s) used to access media 12, to see ifall of them are well-formed, as per information (such as eachstructure's field definition) that is known to data recovery advisor100. The structures that are used to access data in (i.e. store data toand retrieve data from) storage device 12 are also called “storagestructures” as further discussed next.

Storage structures used by data storage system 10 (FIG. 1A) to accessstorage device 12 can have different formats and field definitions,depending on the embodiment. For example, in cases where data storagesystem 10 implements a file system/5819292 for an application (such as abrowser or an accounting package) that is implemented by softwareprogram 11, examples of storage structures include (a) the inode and (b)the file allocation table, or FAT), (c) directories, (d) file systemjournal, and (e) superblocks. Moreover, in cases where data storagesystem 10 implements a database management system, such as ORACLE 10gR1available from ORACLE CORPORATION, examples of storage structuresinclude (a) control file, (b) data file, and (c) log file (such as aredo log). For further details on storage structures in file systems,see U.S. Pat. No. 5,819,292 which is incorporated by reference herein inits entirety.

In some embodiments, an objective of act 101 (FIG. 1A) is to identify atype of failure in media 12, which failure is mapped to a type ofrepair, and the repair type in turn identifies one or more repairs (tobe performed manually or automatically) that can fix data corruption ordata unavailability, and restore health and availability of softwareprogram 11. Specifically, as per FIG. 1A, each of failures 193 is of aspecific type that is associated with one or more repair types, by a map195 in data recovery advisor 100. Most failures 193 are caused byhardware faults, operating system faults, user errors, and/or bugs(errors in programming logic) of the software program 190. However, notall bugs result in one of failures 193. A software bug by itself is nota failure, unless the bug's symptoms are known data failures, withwell-defined repairs. Accordingly, only known problems, which have knownrepairs, are identified by data recovery advisor 100 of someembodiments, as failures in data storage system 10.

Failures identified by data recovery advisor 100 are distinguished fromerrors that occur in data storage system 10 as follows. Each failureunambiguously describes a specific problem (which is one of severalproblems that are known to occur). Determining a root cause of a failure(e.g. faulty disk controller, user error, or a software bug) is notperformed in act 101 of most embodiments. Instead, each failureidentified by act 101 is pre-selected to be of a type that has one ormore known repair(s) which can be used to repair data that isinaccessible or corrupted due to the failure. To better understand thedifference between a failure and an error, the inventors of the currentpatent application recommend the reader to analogize the term “failure”to the term “disease” commonly used in the medical field. In accordancewith the just-described medical analogy, errors (e.g. file open error)of a failure (e.g. missing file) are analogous to symptoms (e.g.sneezing/coughing) of a disease (allergy/cold/flu). Accordingly, each offailures 193 represents a specific conclusion of an analysis, about aproblem of data storage system 10.

Note that any one of failures 194A . . . 194I . . . 194M (togetherreferred to as failures 193) may manifest itself in a number ofobservable symptoms, such as error messages, alarms, failed healthchecks, etc. However, conceptually each failure 1941 is different from asymptom itself because each failure 1941 represents a diagnosed problem(conclusion as to the source of the symptom), and because each failuremust be associated with one or more repairs. Examples of failure(s) 193detected by act 101 include: (a) inaccessible data file, (b) corrupteddata block and so on. Not every fault in computer system 800 is one offailures 193, because a failure 194I only represents a fault that isknown. In addition, as noted above, each failure 194I isdeterministically identifiable, by performing in act 101 one or moreprocedure(s) specifically designed for finding the fault, and as notedabove the fault must be fixable by performing a deterministic repairinvolving a manual or automatic action(s). Note that relationshipsbetween symptoms, failures and underlying faults can be non-trivial, andas noted above they are determined ahead of time, and appropriatelyprogrammed into data recovery advisor 100.

A single fault (which may be a “root” cause) can result in multiplefailures with different symptoms; moreover, a single symptom cancorrespond to multiple failures. Knowing a symptom or a root cause of afailure might not be enough for a human to formulate a specific sequenceof acts (e.g. a repair) to be performed (manually or automatically) torepair a failed component of data storage system 10, which component canbe any of hardware, software or data. Accordingly, only a fault thatindicates the nature of the problem is formulated into a failure (of aparticular type) and is associated with a repair type. Specifically, asnoted above, in reference to map 195 of FIG. 1A, a failure type may beassociated with more than one repair type, if multiple repairs arepossible to address a given failure. Despite the fact that in some casesa failure, its symptom and its root cause can be the same or can beconfusingly similar, each of them represents a different concept andconceptual differences between them are supported by their differenttreatment within the software used to program computer system 800 tofunction as a data recovery advisor 100 of several embodiments.

In performing act 101, data recovery advisor 100 of some embodimentsverifies the integrity of storage structure(s) that are used to storethe data in storage device 12 by implementing physical check(s) and/orlogical check(s) and/or both. Physical checks include checking of one ormore attributes of items that are physical entities, such as a file or ablock. These attributes (also called “physical attributes”) areindependent of the data that is contained within the file or block. Oneexample of a physical check is whether a given file exists, which isimplemented by making a call to the operating system of computer system800. Physical checks can be specific to the type of file or type ofblock. For example, files and directories have different block formatsand therefore have different checks. Accordingly, in act 101 a computer811 (included within computer system 800) is programmed, in someembodiments, to compute and verify a checksum, and verify presence ofone or more known fields such as a predetermined number (i.e. aconstant). In another such check, depending on the type of file (e.g. asindicated by file name and/or an index) computer 811 checks if a headerwithin a first block of the file has a field whose value indicates thesame type.

In addition to (or instead of) checking physical attributes as discussedin the previous paragraph, in some embodiments, the computer (withinsystem 800) is programmed to perform logical checks. Logical checks mayinclude performing range checking. An example of a logical attribute isthe list of file names specified in a directory block. A directory blockmight be correctly formatted, but have an incorrect file name entry.Such a block would pass the physical checks but would fail the logicalcheck. Additional examples of logical checking include: date is valid,size is valid (e.g., does the size stored in the block match thephysical size of the block that has been retrieved), and field is withina valid set of values (e.g., if there is a filetype field in the storagestructure being verified, make sure the value is one of the valid ones).Logical checks may also check relationships between blocks. For example,if there are references, pointers, or offsets from one block to another(as might exist in a file allocation table or database index), thecomputer makes sure that the referenced blocks do exist. In someembodiments of the just-described example, the computer reads the actualreferenced block, to see if that block is correct. For a directory, thecomputer checks to make sure that the file entries in that directoryexist. Depending on the content, the computer can also be programmed toperform checks on the content of the file or block. For example, XMLdocuments have a well-defined structure that is validated in someembodiments. Some embodiments of the computer also do range checking onapplication-specific fields.

After verifying the integrity of storage structure(s) as described abovein reference to act 101, the programmed computer automaticallyidentifies zero, one or more failures. For example, at the end of act101, a failure 1941 that caused one or more errors 13 to occur isidentified. As noted above, a failure 194I which is identified by act101 is of a type that is known ahead of time to act 101, i.e. it is oneof a predetermined set of known types of failures. The identifiedfailures 193 are initially stored by computer system 800 in a volatilememory 806 (see FIG. 8), and eventually followed by transfer to astorage device 810 that stores data persistently, such as a hard disk.In some embodiments, performance of act 101 includes execution of anydiagnostic software that tests the integrity of an item (such as data,hardware or software) in data storage system 10, to ensure that the itembeing tested has its structure and function as expected by softwareprogram 11.

Note that the above-described integrity checking in act 101 is performedafter startup and initialization of software program 11, i.e. duringnormal operation of data storage system 10. The checking of integrity inact 101 may be initiated and/or repeated (as per act 102) asynchronouslyin response to an event in data storage system 10, such as a commandfrom the user or an error encountered by software program 11 in readingor writing data to media 12, depending on the embodiment. Performance ofacts 101 and/or 102 is scheduled in some embodiments to be periodic (atpredetermined time intervals, such as once an hour), or alternativelyaperiodic based on user input, e.g. user specifically schedules act 101to be performed at certain times of the day when data storage system 10is expected to be underutilized.

As illustrated in FIG. 1A, acts 103 and 104 together form an operation121 that decouples a human user's interaction (and therefore theirexperience) from the work performed by computer system 800 in act 101 ofseveral embodiments. Such decoupling has several advantages, as follows.Act 101 is performed automatically asynchronously in the background, soit does not interfere with operation of software program 11 thattriggered performance of act 101 (i.e. software program 11 can continueto operate after logging an error). Moreover, performance of operation121 in response to a user command is also not adversely impacted, aswould happen if performance of act 101 is started only in response to(and subsequent to) act 102 (i.e. user does not have to wait while act101 is being performed). In some embodiments, failures 193 resultingfrom act 101 are stored in a persistent storage device (such as a harddisk), and arise from an automated response (by act 101) to an errorbeing detected.

Note that a storage device to persistently store failures 193 is notused in certain alternative embodiments which simply store failures inmain memory of computer system 800. Moreover, some alternativeembodiments perform act 101 only in response to human input (shown bydashed arrow 199). Note that act 103 is performed in the reverse ordershown in FIG. 1A relative to act 101 in some embodiments, i.e. act 103is performed initially and supplies user data to act 101. Also, in thesome embodiments of the data recovery advisor 100, act 104 is performedonly in response to a command from the user in act 103. However, inalternative embodiments, one or more such acts may be performedautomatically as discussed below in reference to FIG. 1B.

In one embodiment, acts that are performed by computer system 800 afteract 104 depend on the human user. For example, in several embodiments,computer system 800 is programmed to receive from the human user (as peract 105) a selection from among displayed failures, which selectionidentifies a specific failure to be corrected. In response to user'sidentification of a specific failure, computer system 800 automaticallyidentifies (as per act 106) one or more predetermined repairs forcorrupted data in storage media 12.

As noted above, any failure to be recognized by data recovery advisor100 (FIG. 1A) must be associated with repair for fixing the failure. Oneor more types of repairs are automatically identified in act 106, e.g.by use of map 195 which is implemented in some embodiments as a lookuptable. The table (which implements map 195) is static and it is set upahead of time in a memory of computer system 800, during initializationand startup of data recovery advisor 100. Among the identified types ofrepairs, each type of repair is alternative to another type of repair,and consequently the corresponding repairs themselves constitute a groupof alternative repairs, each of which can fix the specific failureselected by the user. Accordingly, in act 107 (FIG. 1A) computer system800 displays to the user, multiple alternative repairs, for repairing auser-selected failure.

As illustrated in FIG. 1A, acts 105, 106 and 107 together constituteanother operation 122. Operation 122 is shown in FIG. 1A as beingcoupled (by a dashed arrow) to operation 121 based on the human user'sinput to computer system 800, in some embodiments. Coupling ofoperations 121 and 122, via input from a human user has severaladvantages, as follows. Firstly, a human user may review failuresdisplayed by act 104 and decide to not take any further action tocorrect any of them at this time (although eventually the user willprobably want to fix all data failures), e.g. if the failures are lessimportant than continuing current operation of software program 190.Therefore, performance of operation 122 is entirely under human controlin these embodiments. Secondly, awaiting user input by such couplingallows computer 100 to only perform operation 122 on those failures thatare selected by the user. Performing operation 122 on selected failuresinstead of doing so on all failures, saves computing resources in theform of processor time and memory. An experienced user may know how tofix a failure just from the detailed description of a failure providedby act 104, and may then fix the failure manually. After such manualrepair, the user can simply issue a command to list failures, which isreceived in act 102 (discussed above) and a record in the repository,for the failure which was manually fixed, is automatically marked asclosed during revalidation in act 103 (i.e. in response command receivedin act 102).

The acts that are performed by computer system 800 after act 107 in someembodiments depend on the human user. In several embodiments, computersystem 800 is programmed to receive from the human user (as per act 108)identification of a selected repair, to fix a corresponding failure. Inresponse to receipt of the user's input in act 108, computer system 800automatically performs the repair identified by the user as per act 109.Accordingly, corrected data that is obtained from repair is stored inmemory (as per act 110), e.g. for later use by software program 190and/or by other software tools and/or by human users. For example, insome embodiments of act 110, computer system 800 is programmed to usethe corrected data from act 109 to overwrite the corresponding corrupteddata in media 12.

In the embodiment illustrated in FIG. 1A, manual selection is made in areal time dialogue between a human user and a computer that implements adata recovery advisor 100 of the type described above. However, in otherembodiments illustrated in FIG. 1B, a selection is made ahead of time,by a user (it's the customer who decides if they want this behavior) whopre-configures the software of a data recovery advisor 100A.Specifically, a data recovery advisor 100A (described below) ispre-configured in certain embodiments to automatically execute a repairthat has no data loss, if such a repair is present in the group ofalternative repairs for the failure.

Accordingly, certain alternative embodiments implement a data recoveryadvisor 100A (FIG. 1B) that automatically performs one or more actswhich otherwise require human input, for example as stated in paragraph[0044] above. Note that certain acts performed by data recovery advisor100A (FIG. 1B) are, in some respects, similar or identical tocorresponding acts performed by data recovery advisor 100 (FIG. 1A),unless described below. For this reason, identical reference numeralsare used in FIGS. 1B and 1A to identify corresponding acts in the twofigures.

Referring to FIG. 1B, human input is not required by data recoveryadvisor 100A prior to operation 122 in some embodiments, which areprogrammed to directly perform an operation 122A automatically, withoutperforming operation 121. Such embodiments are also referred to hereinas “automated” embodiments of data recovery advisor. In operation 122A(FIG. 1B) data recovery advisor 100A automatically selects one or morefailures in repository 196, e.g. at random, in act 105A. In certainembodiments, data recovery advisor 100A is programmed, to use one ormore predetermined criteria and/or predetermined logic for failureselection, to automatically select one or more of failures 193 fromrepository 196.

In some embodiments failures are selected (either automatically or withmanual input as illustrated in FIGS. 1B and 1A respectively) based onpriority, with the highest priority failures being always selected.Specifically, each of failures 193 is assigned a priority (e.g.critical, high, and low) when created. For example, a predeterminedcriterion used in act 105A is to select all failures that are of highestpriority. Note that priority levels are assigned to failures in act 101,by use of a table (not shown) that maps each failure type to acorresponding failure priority. In the certain embodiments, if anyfailures 193 in repository 196 are of priority “critical,” then thesefailures are automatically selected (in the automated embodiment of FIG.1B) or forced to be selected (in the manual-input embodiment of FIG.1A).

Failures with critical priority require immediate attention because theymake software program 11 unavailable. Moreover, failures with highpriority make software program 11 partly unavailable or make data 15partly unrecoverable, and usually have to be repaired in a reasonablyshort time (e.g. within a day). Examples of low-priority failuresinclude data block corruptions in files that are not needed foroperation of software program 11, as well as non-fatal I/O errors.Repair of failures that are of low priority failures can be delayed,until other failures are fixed (delayed either automatically or by theuser). Moreover, some embodiments provide support for a human user toreview and change priorities of failures 193 stored in repository 196.Certain embodiments limit such support, e.g. do not allow lowering ofpriorities, or do not allow lowering the priority of any criticalfailures.

Referring to the automated embodiment of a data repair advisorillustrated FIG. 1B, if there are no critical failures in repository 196then act 105A selects all failures of priority level high. In someembodiments, act 105A additionally selects one or more failures 193 thatdo not have as a prerequisite, fixing of any other failure in repository196 that has not yet been selected. To perform such additionalselection, information about one or more dependencies between eachfailure and any other failure is included in data recovery advisor 100Aof some embodiments, e.g. in a two dimensional table (not shown in FIG.1B).

In the automated embodiment of FIG. 1B in addition to operation 122A,operation 123A is also performed automatically, i.e. all acts of thedata recovery advisor 100A (see acts 105A, 106, 108A, 109, 110 and 111in FIG. 1B) are performed automatically without any human inputwhatsoever. As will be apparent to the skilled artisan, otherembodiments may mix and match acts of FIG. 1A with acts of FIG. 1B, forexample as follows. In several embodiments, after acts 105A and 106 ofFIG. 1B are performed, an act 107 (FIG. 1A) is then performed to displayvarious alternative repairs to a human as illustrated by the embodimentshown in FIG. 1C, followed by acts 108, 109 and 110 as described above,which is then followed by act 111 (described below). Accordingly, in thejust-described embodiment illustrated in FIG. 1C, human input is soughtonly for selection of a repair by performance of acts 107 and 108 ofFIG. 1A, and otherwise performing the acts shown in FIG. 1B. As will beapparent, other embodiments may perform acts 104 and 105 of FIG. 1A toobtain human input on the failures to be fixed, and then perform acts106, 108A, and 109-111 automatically. Hence, numerous such combinationswill be apparent to the skilled artisan in view of this disclosure.

After acts 105A and 106 are performed by an automatic data recoveryadvisor 100A as discussed above in reference to FIG. 1B, and furthermorein some embodiments acts 108A, and 109-111 are also performedautomatically as follows. Specifically, in act 108A, a repair isautomatically selected by data recovery advisor 100A, based on one ormore predetermined criteria and/or predetermined logic for repairselection. For example, in some embodiments, any repairs that do notresult in data loss by performing repair on the data in storage device12 are selected automatically in act 108A. Thereafter, acts 109 and 110are performed in the above-described manner, followed by an act 111 asfollows.

In act 111, automatic data recovery advisor 100A checks if there are anyfailures in repository 196 that need to be fixed (e.g. identified bystatus of “open”). If the answer is yes, then automatic data recoveryadvisor 100A returns to act 105A (described above). If the answer is no,then automatic data recovery advisor 100A waits and then returns to act111. The waiting by automatic data recovery advisor 100A is set by adatabase administrator in some embodiments although in other embodimentsthe duration is of a fixed amount (e.g. 1 second) built into thesoftware of automatic data recovery advisor 100A (e.g. hard codedtherein).

The specific programming of software within data recovery advisor 100and/or 100A will be apparent to the skilled artisan in view of thisdisclosure. However, for illustrative purposes, additional details ofsuch programming are discussed below, in the context of a databasemanagement system (DBMS), although it should be readily apparent thatDBMS is merely an illustrative example of a data storage system 10, andother data storage systems, such as file systems, are also implementedin the manner described herein.

In several embodiments, a computer is programmed to check integrity ofdata in a storage structure from which an error arises in response atleast partially to occurrence of the error during access of the data.Specifically, on occurrence of each error, a method 200 of the typeillustrated in FIG. 2A is performed by computer system 800 to implementflood control at two levels, to account for duplicate errors (within atime period) and for duplicate performance (within another time period)of act 101. As noted above in reference to FIGS. 1A-1C, act 101 performsone or more physical and/or logical checks on data 15. One or more acts201-208 of method 200 may be performed within software program 11 thatuses storage structures to access data 15, or alternatively one or moreof these acts may be performed by data recovery advisor 100/100A/100B,depending on the embodiment.

Specifically, in some embodiments, after an error arises in data storagesystem 10 (hereinafter “current error”), the computer automaticallyperforms act 201 to record occurrence of the current error with a timeand date stamp in a log (also called “first log”). The first log is usedin act 203 as discussed below; and the log is purged on a periodicbasis. After act 201, the computer checks a predetermined set of errors,to see if the current error is of interest as per act 202, and if not ofinterest then returns from method 200.

If in act 202, the computer determines that the current error is ofinterest, then it goes to act 203. In act 203, the computer checks inthe first log whether any prior error recorded therein (as per act 201)is identical to the current error (e.g. same type and same parametervalues), and if so whether that prior error satisfies a predeterminedcondition relative to the current error. For example, the computerchecks if the prior error occurred at least within a first time periodof occurrence of the current error, with the first time period being setat, for example, 5 minutes.

If the answer in act 203 is yes, then the current error is floodcontrolled, i.e. it does not perform act 101. If the answer in act 203is no, the computer goes to act 204 to implement the performance of act101. In some embodiments, act 101 is performed by execution of aprocedure (called “diagnostic procedure”) in a process that is separateand distinct from the process in which the error arose. Note that inother embodiments, the computer does not execute a diagnostic procedure,and instead the integrity checking is done in an in-line manner byperformance of act 101 by the same process that identifies the error.However, decoupling a first process that detects an error from a secondprocess that uses the error to diagnose a failure is advantageousbecause the first process can continue execution without waiting for thesecond process to finish execution.

Accordingly, in act 204 some embodiments use a type of the error thatarose to look up a predetermined table 210 (FIG. 2B), and find theidentity of a diagnostic procedure to be executed. Note that in act 203,instead of (or in addition to) flood controlling of an error based on asingle occurrence with a given time period, other embodiments performflood control based on the number of occurrences of the error within afirst window of time, e.g. 2 times in 10 minutes. Next, in act 205, thediagnostic procedure is instantiated. Specifically, various parametersrelated to the current error are automatically matched, by the computerperforming act 205, to parameters of the diagnostic procedure.

Then in act 206, the computer checks to see if the diagnostic procedureidentified in act 204 has been previously performed within a second timeperiod, e.g. 1 minute and also checks if the diagnostic procedure iscurrently executing. Whether the diagnostic procedure is currentlyexecuting is determined from the value of a flag, which flag is set atthe beginning of execution of the diagnostic procedure as per act 211 inFIG. 2C (described below). Note that in performing act 206 (in a mannersimilar to act 203), instead of (or in addition to) flood controllingexecution of a diagnostic procedure based on its single performance in agiven time period, other embodiments perform flood control based on thenumber of performances of the diagnostic procedure within a secondwindow of time, e.g. two times within 2 minutes.

If the result in act 206 is no, then the computer automatically goes toact 207 and records, in a second log, an identity of the diagnosticprocedure being invoked and the time and date of invocation. This secondlog is used in act 206 (described above), in a manner similar to theabove-described use of the first log in act 203. After act 207, thecomputer performs act 208 to initiate execution of the diagnosticprocedure, e.g. by sending to a background process, a message containingthe diagnostic procedure's identity and its parameters.

FIG. 2C illustrates various acts performed by act 101 when performed bya background process that executes a diagnostic procedure in operation210. Specifically, in act 211, the computer sets a flag to indicatestart of the diagnostic procedure that has been identified by method200. Next, in act 212, the computer verifies the integrity of dataaccessed by certain storage structures, which storage structures areknown to result in the error type that triggered the diagnosticprocedure. In executing the diagnostic procedure, if any failure isfound, the computer goes to act 213 and generates a request to create inthe failure repository, a failure identified by the failure type and oneor more parameters specific to that failure type. In some embodiments,one of the parameters describes an impact of the failure, such as aspecific object in stored data 15 that is not currently available due tothe failure. Values for the parameters of the failure are determined bythe diagnostic procedure based on information (e.g. from an off-linedictionary) that is specific and unique to each failure. Note however,that in certain embodiments, the just-described parameter values are notdetermined from an off-line dictionary, and instead these values aredetermined from an on-line dictionary. Instead in the certainembodiments, an off-line dictionary is used only for impact information.Next, in act 214, the computer generates a report of the failures thathave been found and records in the second log an event indicatingcompletion of the diagnostic procedure. Thereafter, in act 215, thecomputer clears the flag that had been set in act 211 and then waits (inthe background process) for another message from the process of method200, to execute another diagnostic procedure.

Accordingly, a diagnostic procedure is run in some embodiments ofoperation 210 to find out what, if any, problems may be present incertain data components of computer system 800 that may cause an errorwithin software program 11. As noted above, the diagnostic proceduretypically uses technical information about specific data, hardware orsoftware whose integrity is being checked. For example, a diagnosticprocedure for data 15 (FIG. 1A) in storage device 12 may contain one ormore data structures (which define data types of one or more fields)used by software program 11 to access data 15. In this example, thediagnostic procedure type-checks and/or limit-checks data 15, by use ofpredefined storage structure(s), to determine whether a particular fieldtherein has an error.

Also depending on the embodiment, a diagnostic procedure that isexecuted in operation 210 can be configured to diagnose just one failure(e.g. one procedure per failure), or configured to diagnose multiplefailures (e.g. a single procedure for certain failures of a particulartype or particular layer of software, or even a single procedure for allfailures). Moreover, in embodiments that use multiple diagnosticprocedures, the same failure can be diagnosed by several differentdiagnostic procedures, any one or more of which may be performed inoperation 210. Note that in some embodiments, each failure is diagnosedby only one diagnostic procedure, although that one diagnostic procedureitself diagnoses multiple failures.

Further depending on the embodiment, a diagnostic procedure can beexplicitly invoked either by the user or by computer system 800 as partof a scheduled evaluation of data in storage device 12 (FIGS. 1A-1C). Incertain embodiments, execution of a diagnostic procedure in operation210 is automatically started based on occurrence of a correspondingerror in software program 11, e.g. by computer system 800 using anactivation table (not shown in FIG. 1A) that associates errors withcorresponding diagnostic procedures. Moreover, execution of a diagnosticprocedure can be triggered by the output of another diagnostic procedurein operation 210, e.g. by indication of an error.

The specific diagnostic procedures that are used by a DRA of the typedescribed herein will be readily apparent to the skilled artisan. Inparticular, the skilled artisan will be able to use utilities commonlyavailable in the industry to check file systems and databases forconsistency. Moreover, specific repairs depend on the specific datastorage system, and may include getting data (backups, log of changes,etc.) from external sources such as a backup server orstorage/filesystem/database replica. Accordingly, a DRA for file systemsin accordance with this invention is superior to a prior art utilitycalled “fsck”. Without the ability to access external sources, such aprior art utility experiences data loss, which can be avoided by a filesystem DRA of the type described herein. One or more of the integritychecking techniques used by a file system DRA of the type describedherein for UNIX can be implemented in a manner similar or identical tofsck, as described in, for example, an article entitled “Fsck—The UNIX†File System Check Program” by Marshall Kirk McKusick and T. J. Kowalskipublished Oct. 7, 1996 that is incorporated by reference herein in itsentirety. Also, integrity checking techniques used by the file systemDRA for Windows XP (available from Microsoft Corporation) can be toinvoke the operating system utility “Chkdsk”. Moreover, a database DRAmay invoke the checks supported by a database management system, such asDBCC CheckDB.

In some embodiments, a framework within the computer receives therequest generated in act 213 (described above), and performs the methodillustrated in FIG. 2D. Specifically, in act 221, the computer uses afailure type identified in the request to look up a table (not shown)and identify all parameters of the failure. Next, in act 222 thecomputer verifies the parameters, e.g. by checking if the value(received with the request) of each parameter is between predeterminedlimits (max, min) on legal values for that parameter. Next, in act 223,the computer instantiates a failure, by storing in failure repository196 a record for the failure identified by a unique identifier (which isa sequence number that is monotonically changing, e.g. an integer countthat is incremented by 1 for each failure). An illustrative record for afailure in storage device 810 is illustrated in FIG. 2E as discussednext.

In some embodiments, the computer stores for each failure 230 (FIG. 2E),values of several attributes, such as identifier 231 (a unique number),a failure type 232 (a value that is one of several predefined values),creation time 233 (current time and date when failure is stored), status234 (“open” initially, and when failure is fixed, changed to “closed”),priority 235 (for example, critical, high, low), text description 236 (adetailed statement of the failure, to specifically describe the natureof the problem encountered by software program, to enable manualselection of one of several repairs for fixing the failure), parentidentifier 237 (to identify a parent failure into which the currentfailure can be aggregated), and revalidation software's identification238. Identification 238 is used whenever the computer needs to check ifthe current failure is still valid (i.e. data storage system 10 stillhas the current failure).

Although certain failure attributes have been described and illustratedin FIG. 2E as being stored for each failure 230, fewer attributes oreven more attributes may be stored depending on the embodiment. Forexample, the revalidation software's identification 238 is not stored insome embodiments, with each failure. Instead, the revalidationsoftware's identification 238 is stored associated with one or morefailure types, and accordingly each failure's type is used to look upthe revalidation software's identification 238.

In addition to the just-described attributes, a failure may also haveone or more parameters 239 (as discussed above). Failure attributes,parameters, and their values can differ in different systems.

After performing act 223, the computer flags (in act 224) a currentfailure as a duplicate if the same failure was previously recorded infailure repository 196. Specifically in some embodiments of act 224, thecomputer searches the repository for the failure and if a duplicatefailure exists (e.g. same type and same parameter values) and if its'status is open then the current failure is marked as a duplicate. Forexample, if a diagnostic procedure C is executed by act 101 at time Mand detected Failure B. Then some time later at time N (N>M), diagnosticprocedure C is executed by act 101 again and detected Failure B again.Adding Failure B the second time around creates duplicates, which aremarked in repository 196 by some embodiments as being duplicates.However, certain embodiments do not create duplicate failures inrepository 196. For example, a current failure is simply discarded if aduplicate is found in repository 196. As another example, when adiagnostic procedure C starts execution, procedure C automaticallycloses any failures in repository 196 that were previously detected byitself (i.e. by procedure C), so that only newly found failures arerecorded which are unique (as any previously recorded duplicates havebeen closed).

In certain embodiments, the computer is further programmed to aggregatetwo or more failures into a single “aggregated” failure (also called“parent failure”). Hence, when multiple files (or alternatively blocks)used by software program 11 are corrupted, then the user initiallyreceives a display of only a parent failure that summarizes multiplefile corruptions (or alternatively multiple block corruptions). In someembodiments, a human user obtains a display of individual failures thathave been aggregated, by making a further request to display eachfailure that has been aggregated (also called “child” failure)individually.

Accordingly, in act 225 (FIG. 2D) of some embodiments, two or morefailures of the same type but different parameter values are used toformulate a parent failure that is added to repository 196 if the parentfailure didn't already exist therein. If the parent failure alreadyexists, then it is updated with parameter values from the two or morefailures being aggregated by act 225. A parent failure's parametervalues are derived from its child failures. For example, if block 2 isidentified as corrupt by one child and block 9 is identified as corruptby another child, the parent failure identifies blocks 2,9 as beingcorrupt. Alternatively, if the two blocks are both in the same file X,the parent failure may simply state that “file X contains one or moreblock corruptions.”

After one or more failures are recorded in repository 196 by act 223,they may be displayed to a human user, e.g. in response to a usercommand to list failures. Specifically, in act 121 (FIG. 2D), thecomputer of some embodiments retrieves all failures in repository 196and for each failure retrieved automatically checks if a failure'sstatus is open, and further confirms that the failure is not duplicated,and that the failure is not a child of another failure, and if theseconditions are satisfied, displays the failure. Note that in someembodiments, each child failure has as an attribute thereof, a pointerto the parent failure and vice versa. Accordingly, if the user commandis to list failure details, in certain embodiments the parent failure isdisplayed simultaneously with a display of that parent's child failures.In some embodiments, the failures are displayed in priority order, withhighest priority failure being displayed at the top of display 812 (FIG.8), followed by the next highest priority failure, and so on.

In some embodiments, failures identified in act 121 (FIG. 2D) fordisplay to a human are revalidated prior to display. During revalidationin act 121 (FIG. 2D), computer system 800 invokes the softwareidentified by use of the failure type to look up a revalidation softwareidentifier for a given failure in a map, to verify that the failurestill exists in data storage system 10 (FIGS. 1A-1C), and marks as“closed” any failure that no longer exists. The software identified byrevalidation software identifier 238 in certain embodiments is a portionof the software that originally diagnosed the failure. For example, aportion of a given diagnostic procedure that is triggered in response toan error is re-executed during revalidation, to ensure that the failurestill exists. Certain alternative embodiments do not perform a lookup ina map to find the diagnostic procedure for a failure based on failuretype, and instead the diagnostic procedure of the alternativeembodiments initializes (as per act 223 in FIG. 2D) in attribute 238(see FIG. 2E), an identifier of a software portion within the diagnosticprocedure, for use in revalidation of the failure in act 121 (FIG. 2D).Some embodiments support performing revalidation in response to a user'scommand, while other embodiments perform revalidation automatically atcertain times, e.g. after repair of data 15 in storage device 12 (FIGS.1A-1C).

One of the functionalities provided by DRA is automatic generation of aconsolidated repair plan for multiple failures. Specifically, there isoften a need to repair multiple failures at the same time for thefollowing reasons: (a) a single fault (a hardware problem or a usererror) can cause multiple data failures; (b) system administratorsusually postpone fixing of non-critical failures until a maintenancewindow or more appropriate time, and by doing this, accumulate multiplefailures that require repair; (c) often failures are latent and do notmanifest themselves until the user tries to use the affected component,but they might be detected by a diagnostic check started because of adifferent reason.

Devising a successful and efficient repair strategy for multiplefailures can be much more complicated than fixing a single failure.There are two reasons for the complexity. The first one is dependenciesin between repairs and failures that should be taken into account whendetermining the order of failure repairs. These dependencies arespecific to the application. The following types of dependencies canexist for a database:

-   -   a. Dependency in between repairs: a repair might not make sense        if another repair has to be executed as well, e.g. a complete        recovery of a component might not make sense if a point-in-time        recovery of the database has to be executed after.    -   b. Dependency in between failure objects, e.g. a table        corruption should be fixed before an index corruption if the        index belongs to the table.    -   c. Dependency of repair feasibility on another repair, e.g,        repair of filesystem structures may be feasible only after        repair of the volume manager data structures.    -   d. Dependency of repair feasibility on failure, e.g. feasibility        of a datafile repair cannot be determined if the control file is        missing.    -   e. Failure depends on repair: failure can be closed (or become        irrelevant) after a repair execution for another failure, e.g. a        block corruption might disappear after a datafile recovery.    -   f. Dependency on a manual repair: if one of the failures has a        manual repair, it has to be fixed first and then automated        repairs should be considered.        In the first three cases a consolidated repair for all failures        can be generated because all failures have feasible repairs.        However, a certain order of repairs should be enforced. In the        last three cases it is not known at repair generation time        whether all failures can/should be repaired and how. The only        repair for these cases, in some embodiments is to separate        failures that can be repaired at the time, generate a        consolidated repair for them and recommend to the user to repair        these failures first and then repeat the failure-diagnosis and        repair-recommendation cycle.

Another reason for the complexity of a consolidated repair generation isthat usually there are many alternative ways to repair a set offailures, and determining the best alternative can be non-trivial. Forexample, if failure F1 can be fixed by repairs R1, R2 or R3, failureF2—by R2, R3, or R4 and F3—by R3 or R5, there might be multiple ways tofix all the failures together: 1) R1, R4, R5; 2) R2, R5; 3) R3. The morefailures are in the set, the more alternatives should be considered andanalyzed.

Therefore, in general, generation of a consolidated repair for multiplefailures consists of the following steps:

-   -   a. given a set of failures determine which of them can be        repaired at this time    -   b. for these failures, determine a correct order in which they        should be repaired    -   c. consider the failures in this order and for each of them        determine the best repair (minimizing time and data loss)    -   d. optimize the set of selected repairs by:        -   (a) removing repairs that will become not feasible or            redundant because of a previously executed repair;        -   (b) replacing repairs for multiple child failures with a            single repair for the parent failure (e.g. recovery of 20            data blocks with a file recovery) if this repair can be            executed faster;        -   (c) other optimizations maybe possible in particular data            storage systems

To execute these steps all dependencies between failures and repairs aswell as guidelines for choosing optimal repairs are specified inadvance, in some embodiments, by designers of the DRA. Suchspecification, in general, may consist of a significant number ofcomplicated rules and needs to be reconsidered every time a new failureof repair type is added to the system. This might not be feasible forsome data storage systems.

The process of repair generation for multiple failures is simplified insome embodiments by dividing up all possible failure types 321-323 (FIG.3C) into a number of groups 301-305 (FIG. 3A), separately generatingconsolidated repair for each group and possibly merging generatedconsolidated repairs into a single repair. The just-described “divideand conquer” approach is built into a DRA of many data storage systemsby dividing up failures into the following three groups: first group 301is an “access” group for failures related to accessing an input-outputcomponent, such as file resides in an inaccessible file system, filesystem not mounted, file does not have right access permissions, file islocked, or operating system (OS) limit on number of open files reached,or OS out of resources needed to access file, etc. Second group 302 is a“physical” group for failures related to physical data consistency, suchas missing and/or corrupt and/or mutually inconsistent physicalcomponents like files or blocks. Third group 303 is a “logical” groupfor failures related to data consistency, such asmissing/corrupt/inconsistent logical objects like directories, fileextent information, tables, rows, indexes, etc.

If software program 11 uses only one storage device 12, then accessgroup 301 is at a higher level in the relative priority 399 relative toall other groups because no other failures can be fixed until softwareprogram 11 can access storage device 12. Specifically, failures in anygroup (including physical group 302) can be fixed only after failures inaccess group 301 are fixed. Hence, physical group 302 may be set (by thehuman designer) at a lower level in the priority 399, relative to accessgroup 301.

Note, however, that although three groups have been described as beingillustrative for an example of a map, this does not mean that thesethree groups have to be present in any given system in order to practicethis invention. Instead, other embodiments group failures differently,because failure grouping is an optimization that depends on theconfiguration and components of the data storage system, and does nothave to be part of DRA. Accordingly, the number of groups, contents ofthe groups, and the ordering of groups (relative to one another) can bedifferent in different embodiments. For example, some embodiments haveonly two groups (e.g. an “access” group and a “physical” group), whileother embodiments have four groups, five groups, or even ten groups.

Some failure groups (called “floating”) 304 (FIG. 3A), do not havestrict ordering constraints. The only requirement for the floatinggroups is that they have to be processed after a certain failure group,but there is no “before” constraint (e.g. no requirement to processbefore any group). In a database example, log group members can berepaired any time after a database is mounted. Hence log group membersmust be repaired after any repairs that are needed to mount thedatabase, but can be repaired simultaneously with other repairs that arepossible when the database is mounted.

Finally, there could be failures for which repair generation is notconstrained by any other failures or repairs and can be done at anytime. Such failures are combined into the “independent” failure group305 (FIG. 3A). A bad block in a user file is an example of anindependent failure in a file system. Depending on the embodiment, notall failures must be grouped into one of the groups of the relativepriority 399 (FIG. 3A), e.g. some failures may be kept ungrouped, or maybe grouped into another group that is processed independently of thepredetermined order.

In the above-described example illustrated in FIG. 3A, map 300 inaddition to groups 301-303 may also contain a group (not shown on thefigure), namely a “transaction” group, which is specific totransactional data storage systems, e.g. databases. Transaction groupcontains one or more failure types related to inability to process dataduring otherwise normal functioning of software program 11. An examplein this group is a failure in performing a transaction on a database dueto inability to secure a lock on an object. As noted above, failures inany group (including transaction group) can be fixed only after failuresin access group 301 are fixed. Moreover, a transaction group failurecannot be fixed in some cases unless software program 11 is initializedand running. Furthermore, in some embodiments, a single fault can resultin failures in multiple groups (e.g. in all three groups 301, 302 and303), and fixing a failure in a higher level group also fixes one ormore failure(s) in other group(s) that are lower than the higher levelgroup (in the relative priority 399).

In some embodiments, a data recovery advisor performs method 310 (FIG.3B) to create a repair plan. Specifically, in act 311, the computer usesthe failure type, of each failure in a set of failures that are to befixed, with map 300 (FIG. 3A) to identify the group to which eachfailure in repository 196 (FIGS. 1A-1C) belongs. Also in act 311, thecomputer stores each identified group in memory, in an associate withthe corresponding failure. Next, in act 312, the computer selects thehighest level group, from among the identified groups that areassociated with the failures to be fixed. For example, if there are onlytwo failures to be fixed, and one failure is in the logical group andanother failure is in the transaction group, then the open group isselected in act 312.

Thereafter, in act 313, some embodiments automatically prepare at leastone repair plan, for the failures associated with the selected highestlevel group, by use of one or more additional map(s). Specifically, inseveral embodiments of act 313, computer 811 uses a mapping of failuretypes to repair types (see map 195 in FIGS. 1A-1C) to identify therepair types applicable to each specific failure in the selected highestlevel group. Next, computer 811 uses the identified repair type(s) withanother mapping of repair types to repair templates (see map 320 in FIG.3C) to identify at least one repair template in memory for each specificfailure. Computer 811 then instantiates an identified repair template,using one or more parameters 239 (FIG. 2E) to create the specific repairfor each specific failure.

In some embodiments, each failure type is associated with multiplerepair types, and the multiple repair types are pre-arranged in arelative priority with respect to one another, which priority is used toselect a repair (from among repairs that are feasible, for a givenfailure). The priorities are set so that “no data loss” repairs have ahigher priority than “data loss” repairs, and faster repairs have ahigher priority than slower repairs. In one illustrative example, if arepair results in no data loss for fixing a given failure, that repair'srepair type is prioritized ahead of other repairs that result in loss ofdata. In several embodiments, one of the repair types is automaticallyselected in act 313 for each failure type, and the selected repair typeis used to prepare a repair plan. Depending on the embodiment, selectionof a repair type (and consequently the repair) may be based onfeasibility of each of the multiple repairs and/or impact on data 15. Inthe above-described illustrative example of this paragraph, if a no-dataloss repair is feasible, it is automatically selected for fixing thegiven failure, but if it is not feasible then a data loss repair isselected (if feasible). Hence, if a “no data loss” repair for eachfailure is feasible, then all such repairs are selected and used toprepare a repair plan (which as a whole results in “no data loss”). Atleast one repair plan, which includes repairs to fix all failures in theselected highest level group is therefore created and stored in memory806 of computer system 800 at the end of act 313.

In some embodiments, in addition to the above-described repair plan, anadditional repair plan is also prepared and stored in memory 806, in asimilar manner, although the additional repair plan contains repairsthat are alternatives to corresponding repairs for the same failures inthe above-described repair plan. Hence, there are at least twoalternative repair plans in memory 806, in these embodiments, forfailures in the selected highest level group. Repairs for the twoalternative repair plans of such embodiments may be deliberatelyselected based on whether or not they require assistance from a human,i.e. one repair plan may consist of only repairs that can be executedautomatically whereas the other repair plan may consist of repairs thatrequire human assistance. In such embodiments, each repair type is alsomarked (e.g. in map 195) with a flag which explicitly indicates whetheror not the corresponding repair requires human assistance, which flag isused in preparing the two types of repair plans.

In some embodiments, the repair plans are limited to failures in theselected highest level group, although in other embodiments the repairplans may include one or more failures from other groups, e.g. failureswhose repairs are not dependent on repair of failures in any othergroup. Also, some embodiments prepare repair plans to fix failures intwo or more successive groups, e.g. a highest level group, a secondgroup that is immediately below the highest level group, and a thirdgroup immediately below the second group. As noted elsewhere herein, thejust-described groups are certain of those groups (from among groups301-303) which have been identified as containing failures currentlylogged in repository 196 (FIGS. 1A-1C).

In some embodiments, map 320 in main memory 806 associates each failuretype with multiple repair types that are used to generate multiplerepair plans. As illustrated in FIG. 3C, a failure type 321 isassociated in map 320 with two repair types 321A and 321M that arealternatives to one another. Specifically repair type 321A requires nohuman involvement to execute steps for repair identified in acorresponding template 324A. On the other hand, repair type 321Mrequires human assistance, e.g. to load a backup tape, to execute therepair steps identified in the corresponding template 324M. Duringrepair creation in act 313 (of method 310 shown in FIG. 3B), each ofrepair templates 324A, 325A and 326A is customized with parameters 239(FIG. 2E) of the corresponding failures being fixed, to create thecorresponding repairs 331A, 332A and 333A.

After repairs are identified, each repair's feasibility is checked andon being found feasible, the repairs are added to a repair plan 330A inmain memory 806. Each repair 331A, 332A and 333A consists of one or moresteps (not labeled in FIG. 3C), which steps are to be performed in thespecified sequence by computer system 800, with the sequence beingidentified in repair templates 324A, 325A and 326A. Note that thesequence is inherently identified in some embodiments, by the order inwhich steps are specified in a repair template. In some embodiments, arepair 331A also includes a detailed description of the actions to bedone for display to a human user (e.g. in act 359). Act 313 of someembodiments chooses a repair description to include in each repair, froma set of predefined descriptions which are associated with thecorresponding repair templates. Similarly, another repair plan 330M isalso created in act 313, by use of the repair types 321M, 322M and 323Mto identify the corresponding templates 324M, 325M and 326M andcustomize them with failure parameters of the failures being fixed tocreate the respective repairs (not individually shown).

Accordingly, repair plan 330M and repair plan 330A are alternatives toone another, and although only two repair plans are illustrated in FIG.3C, any number of such repair plans may be prepared as described herein.Such alternative repair plans are consolidated in some embodiments, toremove any duplicates and/or redundancies in their repair steps.Thereafter the repair plans are presented to a human user bymanual-input embodiments of data repair advisor (see FIG. 1A), whichthen awaits the human's input on selecting one of the plans. Otherembodiments of data repair advisor automatically select one of therepair plans based on one or more predetermined criteria, e.g. whetherall repairs in a plan can be done automatically. Although feasibilityand impact are used in some embodiments to select one of multiple repairplans, other embodiments may use other factors, to select repairs to beperformed.

In certain embodiments, processor 803 implements method 300 byperforming a number of additional acts, such as acts 351-353 (see method350 in FIG. 3D) prior to above-described act 311, and subsequent toabove-described act 312 performing acts 354-358 to implement act 313.Method 350 also includes several additional acts 359-363 subsequent toabove-described act 313. Referring to FIG. 3D, in act 351, processor 803receives a set of failures that are selected for repair, followed by act352. In act 352, the computer creates in main memory 806, a set ofrepairs that are possible for each failure. Specifically, for a currentfailure, the computer identifies multiple repairs that are associatedwith the current failure's type, by looking up a map 195 (describedabove), and saves the multiple repairs to memory 806, in a temporarystructure (such as a list) for the current failure.

Next, in act 353 (FIG. 3D), the computer performs a feasibility check,on every repair in the temporary structure (e.g. list) for each failurein the set of to-be-fixed failures, and sets a flag for each repairindicating if the repair is feasible or not. To check feasibility of arepair, the computer checks, for example if the repair involves copyinga file that the file to be copied exists in storage device 12 (FIGS.1A-1C). Certain repairs are not feasible at certain times or may becomeinfeasible due to certain conditions, e.g. at the time of act 107automatic repair of a file may be not feasible if the entire file itselfis missing in the computer and no backups are available (e.g. due to itsdeletion by a virus), and accordingly an automatic repair for thisfailure is marked as being not feasible. On the other hand, a repairplan 330 (FIG. 3C) may be prepared to include a manual repair, which maybe feasible. The manual repair may require, for example, restoration ofthe missing file from an offsite backup, which commands may beidentified in a template for the repair. After act 353, acts 311 and 312are performed in the manner described above in reference to FIG. 3B.

After completion of act 312, the computer of some embodiments performsact 313 by using a relative priority 399 of groups of failures(illustrated in map 300 in FIG. 3A) to identify a sequence in whichcertain failures are to be fixed in a current iteration and remainingfailures are left unfixed until a future iteration. Briefly, in act 313,computer 811 identifies failures of highest level group that is selectedto be fixed in a current iteration (followed by failures of a nexthighest level group in a future iteration). Specifically, to identifyfailures to be fixed in the current iteration, the computer performsacts 354-356 in a loop followed by acts 357 and 358 in another loop, asfollows. In act 354, the computer checks the received set of failures(as per act 351) to see if all failures have been processed in the loopand if not, goes to act 355. In act 355, the computer checks if thefailure belongs to a highest level group, and if not returns to act 354(described above). If the result in act 355 is yes, then the computergoes to act 356 to mark the current failure as being selected forrepair, and thereafter returns to act 354. In act 355, if the result isyes, then the computer exits the loop and in several embodiments entersa loop around acts 357 and 358 (described next).

In some embodiments, the computer is programmed to determine (in act357) multiple repairs for every marked failure (selected based on itsgrouping), by use of map 320 (described above in reference to FIG. 3C).Thereafter, the computer (in act 357) checks a feasibility flag (set inact 353) for each of the multiple repairs, and infeasible repairs aredropped from further consideration. From among feasible repairs, thecomputer is programmed to select (for a given repair plan) one ofseveral alternative repairs for each failure, based on impact of eachrepair. For example, some embodiments prepare a repair plan in which allrepairs have “no data loss” as their impact. A repair's impact on lossof data is identified by, for example, performing a lookup of a map 320using the repair type of each repair.

Additionally, each repair's impact on the duration of down time (i.e.unavailability) of software program 11 (or a specified componenttherein) is automatically computed in some embodiments, based onestimates of the size of data in a backup file, and speed ofinput/output peripherals of computer system 800, and/or speed inprocessing of the backup file. For example, the time required to read anoff-line backup file is computed by dividing file size by speed ofinput-output peripheral (e.g. a tape drive). Some embodiments prepareestimates of repair duration using heuristics that are based onstatistics from a previous repair, e.g. of the same repair type. Certainembodiments also take into account parallelism, such as the number ofthreads currently available, number of I/O channels. Several embodimentsfurther account for the bandwidth of the storage device and/or I/Operipheral that contains the backup file. The just-described estimate ofrepair duration is displayed to the user merely to provide a roughindication of the order of magnitude of the down time to enable the userto make a selection from among multiple repair plans. Accordingly, theestimate of down time duration is adequate if accurate to within asingle order of magnitude of actual time required to execute the repair.

Some repairs may have minimal impact or no impact on data 15 (FIGS.1A-1C), e.g. the repairs may cause no data loss and such repairs areselected automatically in some embodiments to be included in a repairplan 330. Alternatively, in certain embodiments, repairs having one typeof impact (e.g. no data loss) are added to one repair plan while repairshaving another type of impact (e.g. no down time for software program11) are added to another repair plan. As noted above, the repair plan(s)are stored in main memory 806 and may be saved to storage device 810 atan appropriate time (e.g. when completed).

A computer 811 is further programmed, as per act 358 of method 350 (FIG.3D), to consolidate repairs in a repair plan, to avoid duplicate repairsand/or redundant repairs. Map 195, which maps failure types to repairtypes, is used in act 358 to determine if any repairs in the repairplan(s) are redundant relative to one another, and if so only one copyof the repair is kept in the repair plan(s) and duplicate copies of thatrepair are deleted. Moreover, a repair plan may contain repairs ofdifferent types (for a given impact, e.g. loss-less repair or data-lossrepair). A data-loss repair for a failure may also fix one or more otherfailures thus making other repairs for these other failures redundant.For example, if a file is inaccessible and will be replaced to fix onefailure, any repairs to fix corruption failure(s) within that file aremade redundant. Hence, in act 358, any redundant repairs are alsoeliminated. As noted above, acts 357 and 358 are repeated in a loop,until all known duplicates and redundancies are eliminated. Afterrepairs for all failures of the highest level group have been added tothe repair plan(s), implementation of act 313 is completed and thecomputer proceeds to acts 359-363 as discussed next.

In some embodiments of method 350, computer 811 uses the repair stepsidentified in a repair plan to generate a repair script for executingthe repairs and store the script (as per act 359) in a repository ondisk. Computer 811 of some embodiments additionally writes the repair tothe repository, including the repair's description and a pointer to therepair script. Computer 811 also writes to the repository, aconsolidated list of suggestions of manual steps to be performed by auser, and the list of failures actually fixed by the repair.

Computer 811 is further programmed in some embodiments, to display asper act 359, the repair plan(s) resulting from act 313 (describedabove). Display of multiple repair plans enables computer 811 to obtainfrom a human a selection of one of the repair plans, followed byperforming act 360 to execute the selected plan. Alternatively act 359is not performed in some embodiments that automatically select therepair plan, e.g. to contain repairs that cause no data loss. In thealternative embodiments, control passes from act 358 directly to act360. Computer 811 is further programmed, to perform act 362 (after act360), wherein the data recovery advisor verifies successful completionof the repairs in the repair plan, and automatically updates the statusto “closed” for any failures that have been fixed by the repair. Hence,failures that are closed (by being fixed) are removed from a currentdisplay of open failures as per act 363.

In one illustrative embodiment, a data recovery advisor is included asone component of certain software (called “recovery manager”) within adatabase management system (DBMS) which is included in a softwareprogram 11 of this embodiment. This embodiment (also called “databaseembodiment”) is illustrated in FIG. 4A by data recovery advisor 400which is included as a portion of a DBMS 490 implemented (in whole or inpart) by software in computer system 800. Accordingly, the human user inthis database embodiment is a database administrator (DBA). Datarecovery advisor 400 automatically diagnoses failures in database 491,and generates a repair plan for fixing as many of the failures aspossible, taking into account dependencies of repairs on one another,and determining an order for repairs that are included in the repairplan. If not all failures of database 491 can be addressed by the repairplan, data recovery advisor 400 recommends performing the repairs in therepair plan in one iteration, followed by another iteration by returningto act 402 (FIG. 4A). DBMS 490 of some embodiments is a relationaldatabase management system which responds to queries from the DBA,expressed in the structured query language (SQL), such as ORACLE® 11 gRelease 1 (11.1), available from ORACLE CORPORATION, Redwood Shores,Calif. (hereinafter simply ORACLE®). Note that the just-described DBMSis referred to below as “ORACLE® 11gR1”.

Although the description below refers to databases and DBMS, several ofthe concepts described below (either individually or in combination withone another) are used in other embodiments for repairing the data of anysoftware programs which are not DBMSs, such as software program 11 whichhas been described above, in reference to FIGS. 1A-1C. Data recoveryadvisor 400 of an illustrative database embodiment which is shown inFIG. 4A automatically diagnoses data failures in database 491,determines and displays to the database administrator (DBA) appropriaterepairs, and then executes a DBA-selected repair. Use of data recoveryadvisor 400 eliminates the need for the DBA to manually correlatevarious symptoms (such as errors) in database 491 in order to diagnose afailure. Note that certain acts performed by data recovery advisor 400(FIG. 4A) are, in some respects, similar or identical to correspondingacts performed by data recovery advisor 100 (FIG. 1A). Hence, referencenumerals in FIG. 4A are derived from corresponding reference numerals inFIG. 1A, by adding 300.

Referring to FIG. 4A, acts 402-410 are performed by data recoveryadvisor 400 in a manner similar or identical to the corresponding acts102-110 (described above). As a repair of a failure might potentiallyhave an impact on the availability, integrity and performance ofdatabase 491, some embodiments of DRA 400 are deliberately designed torequire human input (by someone with DBA privileges) to decide on whichfailures to repair in a current iteration, and which specific repairmechanisms to use during the repair. Accordingly, DRA 400 includes acts402, 405 and 408 which are described below for some embodiments in thecontext of a “LIST” command, a “ADVISE” command and a “REPAIR” commandrespectively. Data repair advisor 400 can be used either through agraphical user interface (called “Enterprise Manager” in ORACLE® 11gR1)or through a command line interface (in recovery manager software called“RMAN” in ORACLE® 11gR1) of a database management system (DBMS).

In the embodiment of FIG. 4A, one or more errors 492 that areencountered by DBMS 490 in using database 491 are used as triggers bydata recovery advisor 400 to automatically initiate in act 401, theexecution of one or more diagnostic procedures 441, whose executablesoftware is available in a storage device 440 (FIG. 4A) included withina computer system 800 (FIG. 8). More specifically, in the embodimentillustrated in FIG. 4A, data recovery advisor 400 uses a first map 430(stored in memory 806 of computer system 800) with an error's identifieras index to look up a corresponding diagnostic procedure's identifier.Thereafter, data recovery advisor 400 uses the diagnostic procedure'sidentifier to initiate execution of diagnostic procedure 441S. Whendiagnostic procedure 441S completes, it stores one or more failures in arepository 494 in a storage device of computer system 800 (FIG. 8).

Many embodiments of the data recovery advisor 400 include a number ofdiagnostic procedures 441A-441N to check for the integrity of thevarious storage structures of database 491. Functions performed by eachof diagnostic procedures 441A-441N depend on specific details of howDBMS 490 is implemented, e.g. specific memory management techniquesand/or storage structures. Note that details of implementation of datarecovery advisor 400 for a specific DBMS 490 are not critical topracticing the invention. Nonetheless, certain descriptions herein referto examples that are implemented for a DBMS available from ORACLE®CORPORATION, such as ORACLE® 11gR1, which are intended to beillustrative and instructive examples, and are not necessary to practicethe invention.

Certain embodiments of data recovery advisor 400 include a diagnosticprocedure 441A that verifies the integrity of database files and reportsfailures if these files are inaccessible, corrupt or inconsistent. Anexample of diagnostic procedure 441A is a database integrity checkprocedure for a database management system available from ORACLE®. Sucha database integrity check procedure may check if a control file existsfor database 491, and if so open the control file and check forphysical-level corruption, e.g. whether or not a newly-computed checksummatches a checksum retrieved from storage. The database integrity checkprocedure also checks the relationship of the control file with otherfiles, e.g. when other files were last updated relative to the controlfile.

In one illustrative example, a sequence number associated with thecontrol file is checked against a corresponding sequence number of adata file, to ensure both files have the same sequence number. If thetwo sequence numbers from the control file and the data file aredifferent, then an appropriate failure is generated, e.g. control filetoo old or data file too old. An example of a sequence number is asystem change number or SCN in a database accessed with the databasemanagement system ORACLE® 11gR1. Some embodiments also check for versioncompatibility, e.g. that the current version number as identified bydatabase 491 is same as or greater than a version number within a headerin the file being checked (at a predetermined location therein).

A database integrity check procedure may also perform additional checks(similar to the just-discussed checks for the control file) on each filethat is identified within control file. For example, DRA may check forthe existence of every datafile that is identified in the control file.Moreover, DRA may verify that the header information recorded in thedatafiles match the corresponding information recorded for those fileswithin the control file.

Several embodiments of the data recovery advisor 400 include anotherdiagnostic procedure 441B to check for integrity of data blocks. In anexample, diagnostic procedure 441B detects corruptions in the disk imageof a block, such as checksum failures, checks for the presence ofpredetermined numbers (constants), and whether block number matches thatblock's actual offset from the beginning of the file. Most corruptionsin the example can be repaired using a Block Media Recovery (BMR)function of the type supported by a DBMS from ORACLE®. In thejust-described example, corrupted block information is also captured ina database view. Note that diagnostic procedure 441B of some embodimentsresponds to the finding of a failure by checking if other relatedfailures exist. For example, in some embodiments, diagnostic procedure441B, on finding one block corruption in a file, proceeds to check ifthere are additional block corruptions in the same file within apredetermined address range around the corrupted block (e.g. within 10MB on either side of the corrupted block). Diagnostic procedure 441B mayalso be programmed to similarly sample a few blocks in other files onthe same disk to further check for block corruption.

Certain embodiments of the data recovery advisor 400 include yet anotherdiagnostic procedure 441C to check for integrity of a file that holdsinformation needed for recovery from a problem in database 491. Thisdiagnostic procedure 441C looks for the file's accessibility andcorruption and reports any issues. In an illustrative example,diagnostic procedure 441C checks files for redo logs maintained by aDBMS from ORACLE®, as well as the files for archive logs, if available.In the just-described example, diagnostic procedure 441C reportsfailures in, for example, archive log and/or redo log.

Furthermore, in some embodiments, when a diagnostic procedure completesexecution, failures that are newly identified are aggregated ifappropriate, with one or more failures 493 that are preexisting infailure repository 494, by a diagnostic framework 496 (FIG. 4C). Priorto aggregation, a preexisting failure in repository 494 that is to beaggregated is revalidated, taking into account any dependencies of thefailure. For example, for a database that is maintained by a DBMS fromORACLE®, corruption of a data file is only relevant if that data file isa part of the database. Hence, revalidation checks that the data file'sentry is present in a control file of database 491, but if it's not thenthe failure (about this data file) is closed.

After a diagnostic procedure completes execution, diagnostic framework496 (FIG. 4C) performs an impact analysis, for example, to identify oneor more objects in database 491 that are unavailable due to the newlyidentified failure(s). Specifically, in some embodiments, impact offailures is assessed to identify what, if any, user-defined objects areaffected, e.g. to identify in database 491, a table to which a corrupteddata block belongs. The table may be identified from lookup table 19 oran off-line dictionary 14 in (FIGS. 1A, 1B) which is deliberately storedoutside of database 491, to ensure that the dictionary is available inthe event that database 491 is unavailable. In some embodiments, adiagnostic procedure 441A (rather than framework 496) includesfunctionality to perform impact analysis for the failures that itdiagnoses, and information about impact is stored in the failurerepository 494, in association with the failure being stored therein.

Also, in the embodiment of FIG. 4A, data recovery advisor 400 uses asecond map 460 (also stored in memory 806 of computer system 800) with afailure's type in act 406, to identify multiple repair types. As notedabove, the multiple repair types are alternatives to one another. Eachrepair type has a static association in map 460 with multiple templates,and one of the templates is selected and instantiated to create a repair(if feasible) in a given repair plan. Hence, the second map 460 is usedin act 406A of certain embodiments, to create multiple repair plans 481,482 that are alternatives to one another. Accordingly, the same failuresare fixed by each of plans 481 and 482, which plans are alternatives toone another. After display of repair plans 481 and 482 (in act 407) tothe user (who's a DBA), a selected repair plan (e.g. plan 481) isreceived in act 408, followed by execution of the selected repair planin act 409. Corrected data resulting from execution of such repairs isstored in memory in act 410 followed by updating the database 491,thereby to eliminate the errors that triggered act 401 (diagnosis offailures).

In a DRA for a database, the failure groups are ordered sequentiallyaccording to the sequence of state transitions that the database makes,e.g. from a “mounted” state to a “recovery” state to an “open” state.Correspondingly, in such embodiments, failures that prevent mounting thedatabase and belong to the “mount” group are repaired before failuresthat belong to the “open” group and prevent opening of the database. SeeFIG. 4B. However, the database can be neither mounted nor open if thedatabase's files are not accessible from a non-volatile storage mediumon which they are persistently stored. Therefore, failures that preventfile access (e.g. network or disk problems) are fixed before any otherfailures. Thus these three failure groups are processed in a relativepriority (FIG. 4B): Access, Mount, Recovery, Open.

As described earlier [00080], there are many dependencies. In view ofthe above-described dependencies, data recovery advisor 400 of severaldatabase embodiments uses five groups 401-406 of failure types asillustrated in FIG. 4B. Examples of database failures in mount group 302are that control information is (a) missing or (b) corrupt or (c) old(relative to another file of database 491 such as a data file used bythe DBMS for system data). Group 404 is arranged within a relativepriority (FIG. 4B) immediately below group 402 Group 402 has higherpriority than Group 404. Fixing failures in Group 404 requires certaininformation including unique identifiers (such as a file name and pathname within the computer, or alternatively a uniform resource locator(URL)) of files of database 491. Without the information from storagestructures accessible through 402, such as a control file for a DBMSfrom ORACLE®, it may not be possible to even identify which files belongto database 491 as needed to fix failures in Group 404. Identity offiles in database 491 is needed, for example, to revalidate certainfailures, e.g. if a data file is missing. Hence, failures related tocontrol information in group 402 need to be fixed before any otherfailures of database 491 are fixed, but after group 401 failures outsideof database 491 are fixed.

Note that the number of groups and what is within each group is veryspecific to the system that is to be repaired. The following sectionsgive some examples of the failure groups used by a DRA for the Oracledatabase. There is no significance to the naming of the groups. Thenames are selected for easy reference to the DRA implementation for theOracle database.

Referring to FIG. 4B, group 404 is for database failures related torecovery information for database 491, such as a redo log for a DBMSfrom ORACLE®. Examples of database failures in group 404 are thatrecovery information is (a) missing or (b) corrupt or (c) old (relativeto another file of database 401). Recovery group 404 is arranged withinrelative priority (FIG. 4B) above open group 403 because recoveryinformation is necessary in order to perform repairs of certain failuresthat prevent opening the database 491.

Also, map 498 (FIG. 4B) for a database embodiment further includes afloating group 405 for failures whose repairs depend only on Accessgroup 401, and for this reason data recovery advisor 400 is programmedto include as many of these repairs as can be added to any repair planfor groups 402-404, e.g. during consolidation in act 406A. Examples offailures in floating group 406 for a database embodiment include afailure in a file which has an identical copy immediately available incomputer system 800, such as a file that is a log member (e.g. redo logsfor a DBMS from ORACLE®). The missing file can be restored at any time(assuming it is accessible), because the DBMS can continue to operateusing the identical copy which is available.

In some embodiments, map 195 (FIGS. 1A-1C) associates each failure typewith multiple repairs (as per act 421 in FIG. 4D), based on repair typesthat are mapped to the failure type in a predetermined map. In oneexample, a failure is that a block is corrupt, then the following threerepairs are possible (in a database accessible through a DBMS fromORACLE®) as follows: (a) block media recovery (BMR) which recovers thatparticular block from backup; (b) data file restore and recover, whichreplaces the entire data file which contains the corrupted block; and(c) database restore and recover which replaces all files of database491. Accordingly, these three repairs are associated with the blockcorrupt failure type in the following specific order (a), (b), and (c),to minimize the amount of work to be done if each of them is feasible,for example. The next step that is done in such embodiments is simpleconsolidation for all repairs of failures within a group (as per act 422in FIG. 4D), wherein for each failure the very first repair which isfeasible is selected (as per act 423). Accordingly, multiple repairs ofa number of objects (such as blocks of a file or files of a database)can be replaced with a single repair of a higher level object (such asthe file, or the database respectively) within which the number ofobjects are contained, if the single repair is faster.

Simple consolidation (as per act 423) assists data recovery advisor 400of some embodiments to rapidly determine (as per act 424), whether thereare loss-less repairs for the failures to be fixed, or if a data lossrepair needs to be done to fix one of them (even though loss-less repairis the goal). Further to the above-described example in the previousparagraph, if another failure is that a redo log group is unavailable,then the following two repairs are possible (in a database accessiblethrough a DBMS from ORACLE®) as follows: (a) restore the redo log fromsomewhere else; (b) database restore and recover up until the missingredo which loses some data. Accordingly, these two repairs areassociated with the redo log group unavailable failure type in thefollowing specific order (a), and (b), so that the loss-less repair (a)has higher priority than the data loss repair (b) if each is feasible.Hence, if a selected repair is a data loss repair then it means thatthere exists no loss-less repair that is feasible, for the given failuretype.

Accordingly, in some embodiments, a failure may require a feasiblerepair that may render redundant other repairs for other failures. Asanother example, block corruption repairs are made redundant (1) by afull database restore and recover repair, and also (2) by a fulldatabase restore and recover to a previous point-in-time (i.e. databasepoint-in-time recovery). Accordingly, as per act 425, data recoveryadvisor 400 of some embodiments eliminates redundant repairs, andreturns to act 422 to check if all repairs have been processed. If theresult of act 422 is yes, then the repair plan is output, e.g. writtento a repository 494, and eventually displayed to a databaseadministrator via a graphical user interface GUI) on display 812 (FIG.8).

Note that in some embodiments, simple consolidation of the typedescribed above is performed in creating a repair plan for only certaingroups, i.e. not all groups. For example, for a database accessiblethrough a DBMS from ORACLE®, simple consolidation is not used togenerate a repair plan for repairs of failures in access group 301 andin control group 304 (see FIG. 4B). The repairs are arranged in therepair plan in an appropriate sequence, which in some cases may be basedon a temporal order in which the failures were created in repository 492while in other cases the repairs are automatically re-arranged relativeto one another, to make the repair plan as a whole comply with apredetermined set of rules on the sequence.

In certain embodiments when more than a predetermined number (e.g. 1000)of block media repairs need to be done for a single file, they areconsolidated into the single data file's restore and recover. Moreover,in the just-described embodiments, since the final outcome of thisconsolidation is a data file restore and recover, this consolidation isperformed prior to the data file consolidation described in the previousparagraph.

Referring to FIG. 4A, data recovery advisor 400 of some embodimentsconsolidates repairs (see act 406A), based on impact. For examplerepairs whose impact creates no data loss are all consolidated into asingle repair plan. Also in act 406A, data recovery advisor 400identifies specific user objects that are impacted by repair, and suchimpacts are displayed to the human user (who's a DBA) in act 407. Anexample of identifying a specific object in displaying impact in act 407is “The Employee table will be offlined”.

Although in some embodiments groupings of failures are used to createrepairs that are included in a repair plan, in other embodiments suchgroups are not used. For example, a repair template is associated incertain embodiments with a specific failure type only and with noneothers, in which case a repair is created (by instantiating thetemplate) at the same time as the failure to which it corresponds.Therefore in some embodiments, repairs are uniquely associated withspecific failures for which they were created, without reference togroups of the type illustrated in FIG. 4B.

Data repair advisor 400 of some embodiments is implemented in multiplecomputers in some embodiments according to a client-server model. Insuch embodiments, data repair advisor 400 includes at least twoportions, namely client side software 400C and server side software 400S(see FIG. 4C). Client side software 400C (also called “client-side DRA”)which interfaces with a human (i.e. a DBA) to provide a display ofdetailed information on failures and alternative repairs, for use by thehuman in making informed decisions. Specifically, client-side DRA 400Cresponds to commands received from a DBA, either through a command lineprompt (see FIG. 7A) or via a graphical user interface (see FIG. 5A).For example, the database management system “ORACLE® 11gR1” supports acommand line prompt via a Recovery Manager (RMAN), and a graphical userinterface via an Enterprise Manager (EM) both of which are used toimplement a client-side DRA.

Client-side DRA 400C of some embodiments also manages the generation,feasibility checking, and execution of certain repairs. In severalembodiments, client-side DRA 400C interfaces to a catalog 435 whichcontains information on which portions of database 491 have been backedup, into which backup files, and information about a storage medium(e.g. tape) that contains the backup files. Note that catalog 435 isphysically included in a computer 811 (see FIG. 8) that executes clientside software 400C. In addition, another computer 813 executes serverside software 400S that works with client-side DRA 400C to recognize andrepair data failures in database 291.

Server side software 400S (also called “server-side DRA”) includessoftware (called “diagnostic framework” 496) which receives errors thatare generated by a database management system (DBMS) in computer 813while accessing database 491, and responds by running one or morediagnostic procedures as necessary. Diagnostic framework 496 stores anyfailure that is identified by the diagnostic procedures it executes,into repository 494 and in doing so, aggregates failures if appropriate,by creating or updating a parent failure. Diagnostic framework 496 mayalso not store a failure into repository 494, if that failure hasalready previously been stored therein.

Accordingly, diagnostic framework 496 avoids storing duplicate failuresin some embodiments of repository 494, whereas other embodiments dostore duplicate failures which are marked as such in repository 494. Insome embodiments, a portion of a diagnostic procedure is re-executed bydiagnostic framework 496 to revalidate stored failures prior to usage(e.g. to display them to the DBA and/or use them to generate repairs).Hence, server-side DRA 400C also includes a failure revalidation module481 that triggers execution of the revalidation software by diagnosticframework 496 appropriately as described herein. One example ofrepository 494 is an automatic diagnostic repository (ADR) which issupported by the database management system “ORACLE® 11gR1”.

Client-side DRA 400C of some embodiments includes a parser (not labeled)that parses a user's input and invokes one of several functionalcomponents, which are implemented as individual drivers for each of thefollowing commands: LIST command 476, CHANGE command 475, ADVISE command474, REPAIR command 473 and VALIDATE command 472. Specifically, thedriver for LIST command 476 interacts with software (called failure &repair data manager) 483 (which is included in server-side DRA 400S) andprovides an interface to repository 494 that holds failures.Accordingly, the driver for LIST command 476 is able to instructserver-side DRA 400S to prepare a list of one or more failures that arecurrently present in repository 494. The list of failures which isgenerated by server-side DRA may be limited, based on informationsupplied by LIST command 476, e.g. to only critical failures or only tofailures related to a specific component of database 491.

Similarly, other above-described commands are also supported by failure& repair data manager 483. For example, arrow 474A illustrates supportto the ADVISE command 474 provided by failure & repair data manager 483in response to one or more failures selected to be fixed (e.g. by theDBA). Failure & repair data manager 483 responds with repairs (includingsteps and descriptions) to fix the identified failure(s) which are thendisplayed by client-side DRA 400C to the DBA. Thereafter, for eachrepair, the driver for ADVISE command 474 invokes (as shown by arrow474B) certain software (called “repair and feasibility manager”) 477that is included in client-side DRA 400C to check feasibility of theproposed repair.

Note that in some embodiments, repair and feasibility manager 477optimizes performance of multiple feasibility checks that involve thesame database object, by performing one feasibility check for thatdatabase object and then copying the result for the remainingfeasibility checks. For example if one repair is ‘BMR on datafile 5block 10’ wherein BMR is an abbreviation for block media recovery whichis a command supported by a DBMS from ORACLE®, and another repair is‘BMR on datafile 5 block 11’, then repair and feasibility manager 477performs a single check for feasibility of BMR on datafile 5, and thenmarks both repairs with the same result.

When a repair is found to be feasible, the driver for ADVISE command 474invokes software in server-side DRA 400S called “repair consolidationmodule” 484, as shown by arrow 474C. Repair consolidation module 484 inturn consolidates repairs that are to be included in a repair plan andstores them in repository 494 which thereafter supplies the repairs backto client computer 811 for display to the DBA, e.g. via the graphicaluser interface. Repairs selected by the DBA are processed by the driverfor the REPAIR command 473, which supplies the repair for execution torepair and feasibility manager 477.

Repair and feasibility manager 477 is responsive to repairs, and ifinvoked by the driver for the ADVISE command performs feasibility checksthat can be performed locally within client computer 811 to confirm thatthe repair is feasible (e.g. checks if the file needed for repair ispresent in catalog 435). Specifically, repair and feasibility manager477 checks if any backup files needed for the repair are identified incatalog 435. Repairs may also be supplied to repair and feasibilitymanager 477 by a driver for REPAIR command 273, in which case thecorresponding repair steps are executed (either locally in computer 811or remotely in server computer 813). For any repairs whose feasibilitycannot be checked, or which cannot be executed locally within clientcomputer 811 repair and feasibility manager 477 supplies the repairs tocertain software within server-side DRA 400S called “execution engine”441S.

Execution engine 441S (FIG. 4C) initiates feasibility checks with servercomputer 813 to see if a repair (specified by repair ID) is feasible.Execution engine 441S supplies the results of feasibility checking tosoftware (called failure & repair data manager) 483, and in certainembodiments the results are stored in volatile memory while otherembodiments store the results in repository 494. Note that executionengine 441S also executes repair steps, by performing varioustransactions on database 291. Additionally, server-side DRA 400S alsoincludes software (called repair consolidation module) 484 thatretrieves all feasible repairs (from memory or from repository asappropriate, depending on the embodiment) to consolidate them to createone or more repair plans (as per acts 358 and 406A described above inreference to FIGS. 3D and 4A respectively). In creating repair plans,repair consolidation module 484 implements use of groups of failures (asper FIG. 4B) to identify the failures to be fixed in a currentiteration.

Diagnostic framework 496 is implemented in a modular manner in someembodiments of the invention, to enable a human developer of server-sideDRA 400S to specify an error and its corresponding diagnostic procedure,in a set of source code files that is compiled into maps and datastructures that are accessible by DRA at runtime. This simplifies theprocess of preparing and maintaining server-side software 400S. Notethat multiple errors can be specified for diagnosis using the samediagnostic procedure.

The specific manner in which data repair advisor 400 is compiled into anexecutable (software and data separated into individual files or datahardcoded into and interspersed within software) relates toimplementation details that change depending on the embodiment, and arenot important to practicing the invention. Also not important topracticing the invention are details about the language in which datarepair advisor 400 is written (e.g. as macro calls or as C languagefunction calls).

In some embodiments, a repair plan that is created by repairconsolidation module 484 is modified by client-side DRA 400C as may benecessary prior to execution. For example, if a data file is to berestored or recovered from backup, a repair manager (RMAN) in a databasemanagement system available from ORACLE® may be designed toautomatically include an initial command to offline the data file priorto the repair, a command to perform the repair, followed by a finalcommand to online the data file.

Use of a data repair advisor to fix a failure is now described inreference to FIGS. 5A-5P which illustrate screens that are displayed toa DBA in some embodiments (whereby the screens are generated byEnterprise Manager in a database management system available fromORACLE®). Specifically, in these embodiments, after an error occurs, theDBA may view the screen of FIG. 5A, which shows the error message ‘Theoperation for starting up the database has failed. Click “View Details”to see the error. You may have to perform a recovery.’ In response, theDBA may click on the View Details hyperlink as shown in FIG. 5A, whichresults in display of the screen illustrated in FIG. 5B. After reviewingstatus details and error messages (such as “ . . . cannot identify/lockdata file 4 . . . ”), the user clicks the OK button at the bottom rightcorner of this screen. In response, the DBA is shown the screenillustrated in FIG. 5C, wherein the DBA may click on the “PerformRecovery” hyper link. After doing so, the DBA is shown the screen ofFIG. 5D, wherein they must enter their user name and password.

Thereafter, the screen of FIG. 5E is displayed, showing that a highpriority failure has been diagnosed by data repair advisor 200. The DBAis prompted to click on the “Advise and Recover” button, and on doing sothe screen of FIG. 5F is displayed. Note that the failure is describedas “One or more non-system data files are missing.” This is an aggregatefailure, and accordingly the DBA may click on a “+” icon under theFailure Description to request a detailed display of the individualfailures. On doing so, the screen of FIG. 5G is displayed, wherein threefailures are all identified as being of high priority. To view therepair strategy recommended by data repair advisor 200, the DBA mustclick on the “Advise” button.

On clicking the “Advise” button, the data repair advisor 200 displays(as per FIG. 5H) two recommendations for repair, both of which ask theDBA to consider manual repairs. Specifically, two files are to berenamed as specified in FIG. 5H. In this example, assume the DBA doesthe requested changes manually, and returns to the screen display as perFIG. 5I. At this stage the DBA may click on the Re-assess Failuresbutton, to see if the manual operations were sufficient. On doing so,data repair advisor 200 revalidates all failures and closes any failurethat has been repaired. Thereafter, the screen of FIG. 5J is displayed,and the DBA may once again click on the +icon to view details of theaggregated failure, which are shown in FIG. 5K.

In the screen of FIG. 5K, the DBA may one again click on the “Advise”button and on doing so, the screen shown in FIG. 5L is displayed.Another file needs to be renamed or moved manually, as per FIG. 5L.Here, assume the user does not wish to do this task manually, then theymay click on the “Continue with Advise” button, in which case the screenof FIG. 5M is displayed. As shown in FIG. 5M, data repair advisor 200has generated an RMAN script. The DBA may click on the “Continue” buttonin FIG. 5M which causes the screen of FIG. 5N to be displayed.

As shown in FIG. 5N, the user may review the script to be executed, andits impact and if acceptable, click on the “Submit Recovery job” button.On doing so, data repair advisor 200 waits for repair script to executeand then displays the results as per FIGS. 5O and 5P. At this stage, asthe repair was successful, the database has been opened. The DBA maynext click the “OK” button (in the screen of FIG. 5P) and on doing sothey are prompted to log into the Enterprise Manager. The DBA may thenproceed with use of the Enterprise Manager in the normal manner, becausethe database has started operating with no errors, at this stage.

FIGS. 6A-6H illustrate screens for an example in which the DBA uses datarepair advisor 200 to diagnose and repair block corruption.Specifically, FIG. 6A is similar to FIG. 5E described above, except thatthe failure in FIG. 6A is for one or more corrupt blocks. In thisscreen, the DBA may click on the “advise and repair” button as notedabove, and on doing so the screen of FIG. 6B is displayed and clickingthe +icon here displays the individual failures as shown in FIG. 6C. TheDBA again clicks on the “Advise” button, resulting in the display of theRMAN script illustrated in FIG. 6D. On clicking the “continue” button,the repairs are displayed, with the impact of each repair, as shown inthe screen of FIG. 6E. On clicking the “submit recovery job”, the screenof FIG. 6F is displayed. After the job has executed, the DBA may clickon the “View Results” button in FIG. 6F to see the job's successfulcompletion in the screen of FIG. 6G. Finally, FIG. 6H illustrates use ofa sql query by the DBA to confirm that the block corruption has beenrepaired.

FIGS. 7A-7G illustrate the above-described example in reference to FIGS.5A-5P, except that in FIGS. 7A-7G the DBA uses data repair advisor 200via the RMAN command prompt.

Data recovery advisor 200 may be implemented in some embodiments by useof a computer (e.g. an IBM PC) or workstation (e.g. Sun Ultra 20) thatis programmed with an application server, of the type available fromOracle Corporation of Redwood Shores, Calif. One or more suchcomputer(s) 811, 813 can be implemented by use of hardware that forms acomputer system 800 as illustrated in FIG. 8. Specifically, computersystem 800 includes a bus 802 (FIG. 8) or other communication mechanismfor communicating information, and a processor 804 coupled with bus 802for processing information. Each of computers 811, 813 includes aprocessor, e.g. computer 811 includes processor 803 while computer 813includes another processor (not shown). Moreover, computers 811 and 813are coupled to one another by any transmission medium that transfersinformation therebetween, such as a local area network or a wide areanetwork.

Computer system 800 also includes a main memory 806, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 802for storing information and instructions to be executed by processor803. Main memory 806 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 803. Computer system 800 further includes a readonly memory (ROM) 804 or other static storage device coupled to bus 802for storing static information and instructions for processor 803. Astorage device 810, such as a magnetic disk or optical disk, is providedand coupled to bus 802 for storing information and instructions.

Computer system 800 may be coupled via bus 802 to a display 812, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 814, including alphanumeric and other keys, is coupledto bus 802 for communicating information and command selections toprocessor 804. Another type of user input device is cursor control 816,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 803 and forcontrolling cursor movement on display 812. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

As described elsewhere herein, incrementing of multi-session counters,shared compilation for multiple sessions, and execution of compiled codefrom shared memory are performed by computer system 800 in response toprocessor 803 executing instructions programmed to perform theabove-described acts and contained in main memory 806. Such instructionsmay be read into main memory 806 from another computer-readable medium,such as storage device 810. Execution of instructions contained in mainmemory 806 causes processor 803 to perform the process steps describedherein. In alternative embodiments, hard-wired circuitry may be used inplace of or in combination with software instructions to implement anembodiment of the type illustrated in any of FIGS. 1A-1C (describedabove). Thus, embodiments of the invention are not limited to anyspecific combination of hardware circuitry and software.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to processor 803 forexecution. Such a computer-readable medium may take many forms,including but not limited to, at least two kinds of storage media(non-volatile storage media and volatile storage media). Non-volatilestorage media includes, for example, optical or magnetic disks, such asstorage device 810. Volatile media includes dynamic memory, such as mainmemory 806. Common forms of storage media include, for example, a flashmemory, a floppy disk, a flexible disk, hard disk, magnetic tape, or anyother magnetic medium, a CD-ROM, any other optical medium, punch cards,paper tape, any other physical medium with patterns of holes, a RAM, aPROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, orany other medium of storage from which a computer can read.

Transmission media includes coaxial cables, copper wire and fiberoptics, including the wires that comprise bus 802. Transmission mediacan also take the form of acoustic or light waves, such as thosegenerated during radio-wave and infra-red data communications.Transmission media includes a carrier wave that is computer readable.

Various forms of computer-readable media, such as a storage device 12(FIGS. 1A-1C) may be involved in supplying the above-describedinstructions to processor 803 (FIG. 8) to implement an embodiment of thetype illustrated in FIG. 2A. For example, such instructions mayinitially be stored on a magnetic disk of a remote computer. The remotecomputer can load such instructions into its dynamic memory and send theinstructions over a telephone line using a modem. A modem that is localto computer system 800 can receive such instructions on the telephoneline and use an infra-red transmitter to convert the receivedinstructions to an infra-red signal. An infra-red detector can receivethe instructions carried in the infra-red signal and appropriatecircuitry can place the instructions on bus 802. Bus 802 carries theinstructions to main memory 806, in which processor 803 executes theinstructions contained therein. The instructions held in main memory 806may optionally be stored on storage device 810 either before or afterexecution by processor 803.

Computer system 800 also includes a communication interface 815 coupledto bus 802. Communication interface 815 provides a two-way datacommunication coupling to a network link 820 that is connected to alocal network 822. Local network 822 may interconnect multiple computers(as described above). For example, communication interface 815 may be anintegrated services digital network (ISDN) card or a modem to provide adata communication connection to a corresponding type of telephone line.As another example, communication interface 815 may be a local areanetwork (LAN) card to provide a data communication connection to acompatible LAN. Wireless links may also be implemented. In any suchimplementation, communication interface 815 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

Network link 820 typically provides data communication through one ormore networks to other data devices. For example, network link 820 mayprovide a connection through local network 822 to a host computer 824 orto data equipment operated by an Internet Service Provider (ISP) 828.ISP 828 in turn provides data communication services through the worldwide packet data communication network 828 now commonly referred to asthe “Internet”. Local network 822 and network 828 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 820and through communication interface 815, which carry the digital data toand from computer system 800, are exemplary forms of carrier wavestransporting the information.

Computer system 800 can send messages and receive data, includingprogram code, through the network(s), network link 820 and communicationinterface 815. In the Internet example, a server 830 might transmit acode bundle through Internet 828, ISP 828, local network 822 andcommunication interface 815. In accordance with the invention, one suchdownloaded set of instructions implements an embodiment of the typeillustrated in FIGS. 1A-1C. The received set of instructions may beexecuted by processor 804 as received, and/or stored in storage device810, or other non-volatile storage for later execution. In this manner,computer system 800 may obtain the instructions in the form of a carrierwave.

Numerous modifications and adaptations of the embodiments describedherein will be apparent to the skilled artisan in view of thedisclosure.

Referring to FIG. 2A, repositories 220, 230, 240, 260 and 293 may belocated outside of database 291 in some embodiments, to ensure theiravailability even when a control file of database 291 becomes corrupted.Also one or more of repositories 220, 230, 240, 260 and 293 may becombined with one another and/or co-located, depending on theembodiment. For example, all repositories 230, 240, 260 and 293 may belocated on a disk that is separate and distinct from the disk on whichdatabase 291 is located. As another example, all of repositories 230,240, 260 and 293 may be located in a file that is separate and distinctfrom files of database 291, although all these files may be located onthe same disk. In the just-described example, the underlying file systemensures that a corruption in a database file does not affect the filecontaining repositories 230, 240, 260 and 293. Also, each ofrepositories 230, 240, 260 and 293 may itself be located in a separatefile, depending on the embodiment. Furthermore, repositories 230 and 240that contain software code may be maintained in a different mediarelative to repositories 260 and 293 that contain data.

Accordingly numerous such modifications and adaptations are encompassedby the attached claims.

Following Subsections A-D are integral portions of the current patentapplication and are incorporated by reference herein in their entirety.Subsections A-D describe new commands that implement a data repairadvisor of the type illustrated in FIGS. 4A-4D, within a recoverymanager in one illustrative embodiment of a database management systemin accordance with the invention. Note that the word “you” in thefollowing attachments refers to a database administrator (DBA).

Subsection A (of Detailed Description) ADVISE FAILURE Purpose

Use the ADVISE FAILURE command to display repair options for thespecified failures. This command prints a summary of the failuresidentified by the Data Recovery Advisor and implicitly closes all openfailures that are already fixed.The recommended workflow is to run the following commands in an RMANsession: LIST FAILURE to display failures, ADVISE FAILURE to displayrepair options, and REPAIR FAILURE to fix the failures.

Prerequisites

RMAN must be connected to a target database. See the CONNECT and RMANcommands to learn how to connect to a database as TARGET.The target database instance must be started. The target database mustbe a single-instance database and must not be a physical standbydatabase, although it can be a logical standby database.In the current release, Data Recovery Advisor only supportssingle-instance databases. Oracle Real Application Clusters (Oracle RAC)databases are not supported.

Usage Notes

Data Recovery Advisor verifies repair feasibility before proposing arepair strategy. For example, Data Recovery Advisor checks that allbackups and archived redo log files needed for media recovery areavailable. The ADVISE FAILURE output indicates the repair strategy thatData Recovery Advisor considers optimal for a given set of failures. TheADVISE FAILURE command can generate both manual and automated repairoptions.

Manual Repair Options

Manual repair options are either mandatory or repair optional. Therepair optional actions may fix the failures more quickly or easily thanautomated repairs. In other cases, the only repair options are manualbecause automated repairs are not feasible. For example, I/O failuresoften cannot be repaired automatically. Also, it is sometimes impossibleto diagnose a failure because insufficient data is returned by theoperating system or the disk subsystem.

Automated Repair Options

Each automated repair option is either a single repair or a set ofrepair steps. When a repair option has a script that contains multiplerepair steps, ADVISE FAILURE generates the script so that the repairsteps are in the correct order. A single repair always fixes criticalfailures together. You must repair critical failures, but you can alsorepair noncritical failures at the same time. You can repair noncriticalfailures in a random order, one by one, or in groups.

Oracle RAC and Data Recovery Advisor

If a data failure brings down all instances of an Oracle RAC database,then you can mount the database in single-instance mode and use DataRecovery Advisor to detect and repair control file, SYSTEM datafile, anddictionary failures. You can also initiate health checks to test otherdatabase components for data failures. This approach will not detectdata failures that are local to other cluster instances, for example, aninaccessible datafile.

Syntax

ADVISE FAILURE [{{ALL|CRITICAL|HIGH|LOW|failureNumber [, failureNumber]. . . }} . . . ] [EXCLUDE FAILURE failureNumber [, failureNumber] . . .]

Semantics

Syntax Element Description ADVISE Displays information for all CRITICALand HIGH FAILURE priority failures recorded in the automatic diagnosticrepository. You can only use ADVISE FAILURE with no repair options whena LIST FAILURE command was previously executed in the current session.Note: If a new failure has been recorded in then diagnostic repositorysince the last LIST FAILURE command in the current RMAN session, thenRMAN issues a warning before advising on CRITICAL and HIGH failures. ALLLists repair options that repair all open failures together. CRITICALLists repair options that repair only critical failures. HIGH Listsrepair options that repair only failures with HIGH priority. LOW Listsrepair options that repair only failures with LOW priority.failureNumber Lists repair options that repair only the specifiedfailures. EXCLUDE Excludes the specified failures from the list. FAILUREfailureNumber

ADVISE FAILURE Command Output

The ADVISE FAILURE output includes the LIST FAILURE output, which isdescribed in ATTACHMENT B below. RMAN presents mandatory and repairoptional manual actions in an unordered list. If manual repair optionsexist, then they appear before automated repair options. Following tabledescribes the output for automated repair options.

Automated Repair Options

Column Indicates Repair The identifier for the automated repair option.option Strategy A strategy to fix the failure with the REPAIR FAILUREcommand. The Data Recovery Advisor always presents an automated repairoption with no data loss when possible. Automated repair options fallinto the following basic categories: Repair with no data loss Repairwith data loss, for example, Flashback Database Note: The ADVISE commandmaps a set of failures to a the set of repair steps that Data RecoveryAdvisor considers to be optimal. When possible, Data Recovery Advisorconsolidates multiple repair steps into a single repair. For example, ifthe database has corrupted datafile, missing control file, and lostcurrent redo log group, then Data Recovery Advisor would recommend asingle, consolidated repair plan to restore the database and performpoint-in-time recovery. Repair A description of the proposed repair. Forexample, the Description proposed repair could be to restore and recoverdatafile 17. Repair The location of an editable script with all repairactions and Script comments. If you do not choose an automated repair,then you can review this script and edit it for use in a manual recoverystrategy.

EXAMPLES Example of Displaying Repair Options for all Failures UsingRecovery Manager

This example shows repair options for all failures known to the RecoveryData Advisor, based on use of the Recovery Manager, which provides thecommand prompt ‘RMAN>’. The example indicates two failures: missingdatafiles and a datafile with corrupt blocks.

RMAN> LIST FAILURE; List of Database Failures Failure ID Priority StatusTime Detected Summary 142 HIGH OPEN 23-APR-07 One or more non-systemdatafiles are missing 101 HIGH OPEN 23-APR-07 Datafile 1:‘/disk1/oradata/prod/ system01.dbf’ contains one or more corrupt blocksRMAN> ADVISE FAILURE; List of Database Failures Failure ID PriorityStatus Time Detected Summary 142 HIGH OPEN 23-APR-07 One or morenon-system datafiles are missing 101 HIGH OPEN 23-APR-07 Datafile 1:‘/disk1/oradata/prod/ system01.dbf’ contains one or more corrupt blocksanalyzing automatic repair options; this may take some time usingchannel ORA_DISK_1 analyzing automatic repair options complete MandatoryManual Actions no manual actions available Repair optional ManualActions 1. If file /disk1/oradata/prod/users01.dbf was unintentionallyrenamed or moved, restore it Automated Repair options Repair optionRepair Description 1 Restore and recover datafile 28; Perform blockmedia recovery of block 56416 in file 1 Strategy: The repair includescomplete media recovery with no data loss Repair script:/disk1/oracle/log/diag/rdbms/prod/prod/hm/reco_660500184.hm

Subsection B (of Detailed Description)

LIST failure

Purpose

Use the generic LIST command to display backups and information aboutother objects recorded in the Recovery Manager (RMAN) repository.

Prerequisites

Execute LIST only at the RMAN prompt. Either of the following twoconditions must be met: (1) RMAN must be connected to a target database.If RMAN is not connected to a recovery catalog, and if you are notexecuting the LIST FAILURE command, then the target database must bemounted or open. If RMAN is connected to a recovery catalog, then thetarget database instance must be started. (2) RMAN must be connected toa recovery catalog and SET DBID must have been run.

Usage Notes

With the exception of the LIST FAILURE command, the generic LIST commanddisplays the backups and copies against which you can run CROSSCHECK andDELETE commands.The LIST FAILURE command displays failures against which you can run theADVISE FAILURE and REPAIR FAILURE commands.RMAN prints the LIST command's output to either standard output or themessage log, but not to both at the same time.

Syntax

LIST {DB_UNIQUE_NAME {ALL|OF DATABASE [[′] database_name [′]]}|EXPIRED{listObjectSpec [{{maintQualifier|recoverableClause}} . . .]|recordSpec} [forDbUniqueNameRepair option]|FAILURE[{{{ALL|CRITICAL|HIGH|LOW|failureNumber [, failureNumber] . . .}|CLOSED}} . . . ] [EXCLUDE FAILURE failureNumber [, failureNumber] . .. ] [DETAIL]|INCARNATION [OF DATABASE [[′] database_name[′]]]|{{listObjectSpec [{{maintQualifier|recoverableClause}} . . . ]|recordSpec}|RESTORE POINT restore_point_name|RESTORE POINT ALL}[forDbUniqueNameRepair option]|[{ALL|GLOBAL}] SCRIPT NAMES}

Semantics

Syntax Element Description FAILURE Lists failures recorded by the DataRecovery Advisor. The database to which RMAN is connected must be asingle-instance database and must not be a physical standby database.The Data Recovery Advisor can detect and repair a wide variety ofphysical problems that cause data loss and corruption. Physicalcorruptions are typically caused by faulty I/O subsystems or humanerror. The Data Recovery Advisor may not detect or handle some types oflogical corruptions. Corruptions of this type require help from OracleSupport Services. In the context of Data Recovery Advisor, a failure isa persistent data corruption that is mapped to a set of repair actions.Data failures are detected by checks, which are diagnostic proceduresthat asses the health of the database or its components. Each check candiagnose one or more failures, which are mapped to a set of repairs. Thetypical use case is to run LIST FAILURE to list any failures, then useADVISE FAILURE to display repair options, and REPAIR FAILURE to fix thefailures. Run these commands in the same RMAN session. If no repairoptions are specified on LIST FAILURE, then the command lists only thehighest priority failures that have status OPEN. Therefore, CRITICAL andHIGH failures are always listed in the command output if they exist.Failures with LOW priority are listed only if no CRITICAL or HIGHpriority failures exist. Failures are sorted in reverse order ofoccurrence, with the most recent failure listed first. The LIST FAILUREcommand does not initiate checks to diagnose new failures; rather, itlists the results of previously executed assessments. Thus, repeatedlyexecuting LIST FAILURE will reveal new failures only if the databaseautomatically diagnosed them in response to errors that occurred inbetween command executions. However, LIST FAILURE revalidates allexisting failures when the command is issued. If a user fixed failuresmanually, or if the failures were transient problems that disappeared,then Data Recovery Advisor removes these failures from the LIST FAILUREoutput. ALL Lists failures with all priorities and status OPEN. CRITICALLists only critical failures with status OPEN. HIGH Lists only failureswith HIGH priority and status OPEN. LOW Lists only failures with LOWpriority with status OPEN. failureNumber Specifies the failures byfailure number. CLOSED Lists only closed failures. EXCLUDE Excludes thespecified failures from the list. FAILURE failureNumber DETAIL Listsfailures by expanding the consolidated failure. For example, if multipleblock corruptions existed in a file, then specifying the DETAIL repairoption would list each of the block corruptions.

Display of List of Failures

Column Indicates Failure The unique identifier for a failure. IDPriority The priority of the failure: CRITICAL, HIGH, or LOW. Failureswith critical priority require immediate attention because they make thewhole database unavailable. Typically, critical failures bring down theinstance and are diagnosed during the subsequent startup. The databaseis not available until all critical failures are fixed (see ADVISEFAILURE). Failures with HIGH priority make a database partiallyunavailable or unrecoverable, and usually have to be repaired in areasonably short time. Examples of such failures include physical datablock corruptions, nonfatal I/O errors, missing archived redo log filesor backup files, and so on. Failures with LOW priority can be ignoreduntil more important failures are fixed. For example, a block corruptionwill be initially assigned a high priority, but if this block is notimportant for the database availability, you can use CHANGE FAILURE tochange the priority to LOW. Status The repair status of the failure. Thestatus of a failure is OPEN (not repaired) until the appropriate repairaction is invoked. The failure status changes to CLOSED when the repairis completed. Time The date when the failure was diagnosed. DetectedSummary Summary of the failure.

Example of Listing Failures

This example lists all failures regardless of their priority. If you donot specify ALL, then LIST FAILURE output does not include failures withLOW priority.

RMAN> LIST FAILURE ALL; List of Database Failures Failure ID PriorityStatus Time Summary 142 HIGH OPEN 23-APR-07 One or more non-systemdatafiles are missing 101 HIGH OPEN 23-APR-07 Datafile 1:‘/disk1/oradata/ prod/system01.dbf’ contains one or more corrupt blocks

Subsection C (of Detailed Description) CHANGE Purpose

Use the CHANGE command to perform the following tasks:

-   -   Update the availability status of backups and copies recorded in        the Recovery Manager (RMAN) repository    -   Change the priority of or close failures recorded in the        automatic diagnostic repository    -   Update the DB_UNIQUE_NAME recorded in the recovery catalog for        the target database    -   Associate the backup of a database in a Data Guard environment        with a different database in the environment

Prerequisites

RMAN must be connected as TARGET to a database instance, which must bestarted.

Semantics

This command enables you to change the status of failures. Use the LISTFAILURE command to show the list of failures.

Syntax Element Description FAILURE Enables you to change priority orclose failures recorded in the Automatic Diagnostic Repository. Bydefault RMAN prompts for confirmation before performing the requestedchange. The target database to which RMAN is connected must be asingle-instance database and must not be a physical standby database.ALL Changes only open failures. CRITICAL Changes only critical failures.HIGH Changes only failures with HIGH priority. LOW Changes only failureswith LOW priority. failnum Changes only the specified failure. EXCLUDEExcludes the specified failures from the change. FAILURE failnum

Example of Changing the Status of a Failure

In the following example, the LIST FAILURE command shows that a datafilehas corrupt blocks. The failure number is 5 and has a priority of HIGH.You decide to change the priority of this failure to low.

List of Database Failures Time Failure ID Priority Status DetectedSummary RMAN> LIST FAILURE; 5 HIGH OPEN 11-DEC-06 datafile 8 containscorrupt blocks RMAN> CHANGE FAILURE 5 PRIORITY LOW; 5 HIGH OPEN11-DEC-06 datafile 8 contains corrupt blocks Do you really want tochange the above failures (enter YES or NO)? YES changed 1 failures toLOW priority

Subsection D (of Detailed Description) REPAIR FAILURE Purpose

Use the REPAIR FAILURE command to repair database failures identified bythe Data Recovery Advisor.The recommended workflow is to run LIST FAILURE to display failures,ADVISE FAILURE to display repair options, and REPAIR FAILURE to fix thefailures.

Prerequisites

The target database instance must be started. The database must be asingle-instance database and must not be a physical standby database.Make sure that at most one RMAN session is running the REPAIR FAILUREcommand. The only exception is REPAIR FAILURE . . . PREVIEW, which ispermitted in concurrent RMAN sessions.To perform an automated repair, the Data Recovery Advisor may requirespecific backups and archived redo logs. If the files needed forrecovery are not available, then the recovery will not be possible.

Usage Notes

Repairs are consolidated when possible so that a single repair can fixmultiple failures. The command performs an implicit ADVISE FAILURE ifthis command has not yet been executed in the current session.RMAN always verifies that failures are still relevant and automaticallycloses fixed failures. RMAN does not attempt to repair a failure thathas already been fixed, nor does it repair a failure that is obsoletebecause new failures have been introduced since ADVISE FAILURE was run.By default, REPAIR FAILURE prompts for confirmation before it beginsexecuting. After executing a repair, RMAN reevaluates all existingfailures on the chance that they may also have been fixed.

Oracle RAC and Data Recovery Advisor

If a data failure brings down all instances of an Oracle RAC database,then you can mount the database in single-instance mode and use DataRecovery Advisor to detect and repair control file, SYSTEM datafile, anddictionary failures. You can also initiate health checks to test otherdatabase components for data failures. This approach will not detectdata failures that are local to other cluster instances, for example, aninaccessible datafile.

Syntax

REPAIR FAILURE [USING ADVISE REPAIR OPTION integer] [{{NOPROMPT|PREVIEW}} . . . ]

Semantics

Syntax Element Description REPAIR FAILURE Repairs failures recorded inthe Automated Diagnostic Repository. If you execute REPAIR FAILURE withno other command repair options, then RMAN uses the first repair optionof the most recent ADVISE FAILURE command in the current session. Thecommand performs an implicit ADVISE FAILURE if this command has not yetbeen executed in the current session. USING ADVISE Specifies a repairoption by its repair option REPAIR OPTION number (not its failurenumber). You can obtain integer repair option numbers from the ADVISEFAILURE command. NOPROMPT Suppresses the confirmation prompt. This isthe default repair option if you run REPAIR FAILURE in a command file.PREVIEW Does not make any repairs and generates a script with all repairactions and comments. By default the script is displayed to standardoutput. You can use the SPOOL command to write the script to an editablefile (see example of previewing repair below)

Example of Repairing Failures

This example repairs all failures known to the Recovery Data Advisor.The example repairs two failures: missing datafiles and a datafile withcorrupt blocks. After the recovery, RMAN asks whether it should open thedatabase.

RMAN> LIST FAILURE; List of Database Failures Failure ID Priority StatusTime Detected Summary 142 HIGH OPEN 23-APR-07 One or more non-systemdatafiles are missing 101 HIGH OPEN 23-APR-07 Datafile 1:‘/disk1/oradata/prod/ system01.dbf’ contains one or more corrupt blocksRMAN> ADVISE FAILURE; List of Database Failures Failure ID PriorityStatus Time Detected Summary 142 HIGH OPEN 23-APR-07 One or morenon-system datafiles are missing 101 HIGH OPEN 23-APR-07 Datafile 1:‘/disk1/oradata/prod/ system01.dbf’ contains one or more corrupt blocksanalyzing automatic repair options; this may take some time usingchannel ORA_DISK_1 analyzing automatic repair options complete MandatoryManual Actions no manual actions available Repair optional ManualActions 1. If file /disk1/oradata/prod/users01.dbf was unintentionallyrenamed or moved, restore it Automated Repair options Repair optionRepair Description 1 Restore and recover datafile 28; Perform blockmedia recovery of block 56416 in file 1 Strategy: The repair includescomplete media recovery with no data loss Repair script:/disk1/oracle/log/diag/rdbms/prod/prod/hm/reco_660500184.hm RMAN> REPAIRFAILURE; Strategy: The repair includes complete media recovery with nodata loss Repair script:/disk1/oracle/log/diag/rdbms/prod/prod/hm/reco_475549922.hm contents ofrepair script:   # restore and recover datafile   sql ‘alter databasedatafile 28 offline’;   restore datafile 28;   recover datafile 28;  sql ‘alter database datafile 28 online’;   # block media recovery  recover datafile 1 block 56416; Do you really want to execute theabove repair (enter YES or NO)? YES executing repair script sqlstatement: alter database datafile 28 offline Starting restore at23-APR-07 using channel ORA_DISK_1 channel ORA_DISK_1: starting datafilebackup set restore channel ORA_DISK_1: specifying datafile(s) to restorefrom backup set channel ORA_DISK_1: restoring datafile 00028 to/disk1/oradata/prod/users01.dbf channel ORA_DISK_1: reading from backuppiece /disk2/PROD/backupset/2007_04_18/o1_mf_nnndf_TAG20070418T182042_32fjzd3z_.bkp channel ORA_DISK_1: piecehandle=/disk2/PROD/backupset/2007_04_18/o1_mf_nnndf_TAG20070418T182042_32fjzd3z_.bkp tag=TAG20070418T182042channel ORA_DISK_1: restored backup piece 1 channel ORA_DISK_1: restorecomplete, elapsed time: 00:00:03 Finished restore at 23-APR-07 Startingrecover at 23-APR-07 using channel ORA_DISK_1 starting media recoverymedia recovery complete, elapsed time: 00:00:01 Finished recover at23-APR-07 sql statement: alter database datafile 28 online Startingrecover at 23-APR-07 using channel ORA_DISK_1 searching flashback logsfor block images until SCN 429690 finished flashback log search,restored 1 blocks starting media recovery media recovery complete,elapsed time: 00:00:03 Finished recover at 23-APR-07 repair failurecomplete

Example of Previewing a Repair

The following example previews a repair of the first repair option ofthe most recent ADVISE FAILURE command in the current session. Note thatthe sample output for the LIST FAILURE and ADVISE FAILURE commands isnot shown in the example.

RMAN> LIST FAILURE; . . . RMAN> ADVISE FAILURE; . . . RMAN> REPAIRFAILURE PREVIEW; Strategy: The repair includes complete media recoverywith no data loss Repair script:/disk1/oracle/log/diag/rdbms/prod/prod/hm/reco_3200987003.hm contents ofrepair script:   # block media recovery   recover datafile 1 block56416;You can use SPOOL in conjunction with REPAIR FAILURE . . . PREVIEW towrite a repair script to a file. You can then edit this script andexecute it manually. The following example spools a log a repair previewto /tmp/repaircmd.dat.

RMAN> SPOOL LOG TO ‘/tmp/repaircmd.dat’; RMAN> REPAIR FAILURE PREVIEW;RMAN> SPOOL LOG OFF;

1. A computer-implemented method to diagnose and fix a plurality ofpredetermined failures related to a data storage system, said datastorage system being implemented at least partially by a computer, saiddata storage system comprising a plurality of storage structures, eachstorage structure comprising data stored persistently in non-volatilestorage media of the data storage system, the method comprising:checking integrity of data in a storage structure among the plurality ofstorage structures, to identify a set of failures related to saidstorage structure, each failure in said set of failures being one ofsaid plurality of predetermined failures; identifying, based on said atleast one failure in said set, a group of repairs to fix said at leastone selected failure, each repair in the group being alternative toanother repair in the group; executing at least one repair in said groupto generate corrected data to fix said at least one failure in said datastorage system; and storing said corrected data in non-volatile storagemedia of the data storage system.
 2. The method of claim 1 furthercomprising: storing in memory, said set of failures including saidfailure; receiving, from a human, a command to display failures; anddisplaying to said human at least a subset of failures within the set offailures, in response to said receiving of said command.
 3. The methodof claim 2 further comprising: receiving from the human, identificationof said at least one failure.
 4. The method of claim 1 wherein saidstoring further comprises saving to said memory, for each failure: apriority of said each failure; and a status of said each failureselected from a group consisting of (open and closed).
 5. The method ofclaim 1 further comprising, prior to said identifying: selecting said atleast one failure for being of highest priority in said set.
 6. Themethod of claim 1 wherein: said checking is performed periodically. 7.The method of claim 1 wherein: said checking is performed in response toreceipt of a command from a human.
 8. The method of claim 1 furthercomprising, prior to said executing: displaying to a human, the group ofrepairs obtained from said identifying; and receiving from the human,identification of said at least one repair.
 9. The method of claim 1further comprising, prior to said executing: selecting said at least onerepair for being of highest priority in said group.
 10. The method ofclaim 1 wherein: said data storage system comprises a databasemanagement system; and a plurality of storage structures of saiddatabase management system comprise files and data structures of adatabase.
 11. The method of claim 1 further comprising: checkingfeasibility of each repair in said group of repairs prior to saidexecuting.
 12. The method of claim 1 further comprising: estimating animpact of executing a repair script corresponding to said at least onerepair prior to said executing.
 13. A database management system,implemented at least partially by a computer, to correct a plurality ofpredetermined errors that corrupt data in a database in the computer,the database management system comprising: means for responding tooccurrence of an error in the database from among the plurality ofpredetermined errors, by initiating execution in said computer of adiagnostic procedure associated with said error; means for identifying agroup of repairs to fix the data in the database corrupted by thefailure; wherein each repair in said group of repairs is alternative toanother repair in said group of repairs; wherein said group of repairsis automatically identified by the means for identifying, from among aplurality of predetermined groups of repairs, by use of a second map;wherein each failure in the predetermined set of failures is mapped, bythe second map, to a corresponding group of repairs in the plurality ofpredetermined groups of repairs, and each repair in the plurality ofpredetermined groups of repairs is associated with a template for arepair script; means for checking feasibility of each repair in saidgroup of repairs; means for estimating an impact of executing a repairscript corresponding to an repair in a subgroup of repairs; wherein thesubgroup of repairs is selected by the means for checking for beingfeasible, from among said group of repairs; and means for storing inmemory, each repair in said subgroup of repairs obtained from said meansfor checking, and a corresponding impact obtained from said means forestimating.
 14. A computer-readable storage medium comprisinginstructions to a computer to diagnose and fix a plurality ofpredetermined failures related to a data storage system, thecomputer-readable storage medium comprising: instructions to checkintegrity of a storage structure in said data storage system, toidentify a set of failures related to said storage structure, eachfailure in said set of failures being one of said plurality ofpredetermined failures; instructions to identify, based on at least onefailure selected from said set, a group of repairs to fix said at leastone failure, each repair the group being alternative to another repairin the group; and instructions to execute a repair selected from thegroup of repairs, to generate corrected data in a memory of saidcomputer to fix said at least one failure in said data storage system.15. The computer-readable storage medium of claim 14 wherein at least agroup of failures within said set of failures is marked open, thecomputer-readable storage medium further comprising: instructions torevalidate each failure in said group of failures; and instructions tomark said each failure as closed if said instructions to revalidate findsaid each failure no longer exists in said computer.
 16. Thecomputer-readable storage medium of claim 14 further comprising:instructions to display on a screen of said computer an estimate of aduration to perform at least one repair in said group of repairs. 17.The computer-readable storage medium of claim 14 further comprising:instructions to search a repository in said computer for another failureof same type and same parameter values as a current failure; andinstructions to mark in said repository said current failure as aduplicate if said another failure is found to exist in said repositoryand has a status of open.
 18. The computer-readable storage medium ofclaim 14 further comprising: instructions to display to a human at leasta subset of failures within the set of failures; instructions to receivefrom the human, identification of at least one selected failure to befixed, identified from among the subset of failures being displayed. 19.The computer-readable storage medium of claim 14 further comprising:instructions to display to a human, the group of repairs obtained fromexecuting said instructions to identify; instructions to receive fromthe human, identification of a selected repair, selected from among thegroup of repairs being displayed.
 20. The computer-readable storagemedium of claim 14 further comprising: instructions to store saidcorrected data in non-volatile storage media of the data storage system,using at least one storage structure in said plurality of storagestructures.
 21. The computer-readable storage medium of claim 14 furthercomprising: instructions to invoke performance of said instructions tocheck, in response to receipt of a command from a human.
 22. Thecomputer-readable storage medium of claim 14 wherein: said data storagesystem comprises a database management system; and said storagestructure is comprised in a database in said computer accessible viasaid database management system.